Anticancer therapeutic intervention

ABSTRACT

The present invention is directed to a method of treating cancer using interfering RNA duplexes to mediate gene silencing. The present invention is also directed to interfering RNA duplexes and vectors encoding such interfering RNA duplexes.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jul. 16, 2019, is named C64-026732_US_ORD_SL.txt and is 130,450 bytes in size.

FIELD OF THE INVENTION

The present invention is directed to a method of treating cancer using interfering RNA duplexes to mediate gene silencing. The present invention is also directed to interfering RNA duplexes and vectors encoding such interfering RNA duplexes.

DESCRIPTION OF RELATED ART

Regardless of their origin, tumours require a constant supply of nutrients to support their characteristic unabated growth. In fact, tumour cells may consume more nutrients than required for their own metabolic needs (Medina et al., 1992b), and exhibit distinct metabolic profiles compared to their normal cellular counterparts. Tumours are supplied with nutrients to fuel their metabolic needs through the collective processes of angiogenesis and the prodigious expression of nutrient transporters in the plasma membranes of constituent cells. Amino acids are the primary source of cellular nitrogen, used for nucleotide, glutathione, amino sugar and protein synthesis. The voracious and apparently wasteful amino acid metabolism of malignant tumours leads to, among other things, negative nitrogen balance in the host with cancer. Moreover, the carbon skeletons of amino acids are often utilized as an oxidative fuel source for ATP generation in addition to glucose and fatty acids, and may also contribute to sterol and lipid biosynthesis (Baggetto, 1992; Medina et al., 1992a). Compared to normal cells or tissues, cancer cells display enhanced and altered channelling of amino acids into select metabolic pathways, often in concert with the aerobic glycolysis characteristic of tumours (Baggetto, 1992) and (Mazurek et al., 2003). Solid tumours are often poorly vascularized, especially in the nascent avascular phase characteristic of neoplasia and metastases, so they must have efficient mechanisms for extracting plasma amino acids in order to compete with host tissues (Medina et al., 1992b). Cancer, in turn, is a microcosm of evolution, with the “fittest” cells enduring through adaptation to the local microenvironment; as a result, amino acid transporters with properties that impart growth and survival advantages are selected for and expressed, often at augmented levels compared to the parent tissue.

Prior to the advent of mammalian amino acid transporter cloning and isolation, Christensen proposed that specific amino acid transporters could be upregulated in transformed cells to support the high levels of protein synthesis necessary for growth and proliferation (Christensen, 1990). A search of the human expressed sequence tag (EST) database at the Cancer Genome Anatomy Project (CGAP) website (cgap.nci.nhi.gov), using the “cDNA Virtual northern” tool to determine the expression levels of the classic neutral amino acid transport “systems” A, ASC, L and N, in normal and cancerous tissues revealed that while five transporters are significantly enhanced overall in cancerous tissues, two stand out—LAT1 (large neutral amino acid transporter 1) and ASCT2 (ASC amino acid transporter 2) (Fuchs et al., 2005). ASCT2 and LAT1 are both upregulated three-fold (collectively) in a variety of cancerous tissues where their expression pattern is almost identical (Fuchs et al., 2005).

LAT1 has long been associated with cancerous or proliferative cells. When full-length LAT1 was first isolated and characterized in 1998, it was shown not to be expressed in rat liver but was detected in rat hepatoma (dRLh-84) and hepatocarcinoma (FAA-HTC1) cell lines (Kanai et al., 1998), which is consistent with the expression pattern of ASCT2 in human liver as discussed below. Northern blot analysis with human cell lines revealed TA1 expression in the choriocarcinoma cell line JEG-3 and breast carcinoma cell line MDA-A1 (Sang et al., 1995), as well as in stomach signet ring cell carcinoma (KATOIII), lung small cell carcinoma (RERF-LC-MA) and malignant melanoma (G-361) (Kanai et al., 1998). Both 4F2hc and LAT1 were detected in several leukemia cell lines, RERF-LC-MA lung small cell carcinoma cells, HeLa uterine cervical carcinoma cells and T-24 bladder carcinoma cells (Yanagida et al., 2001). The results with the T-24 cells have been confirmed by confocal immunofluorescence microscopy, which revealed colocalization of LAT1 and 4F2hc in the plasma membrane (Kim et al., 2002). LAT1 and 4F2hc have also been shown to colocalize in the plasma membrane of KB human oral epidermoid carcinoma cells (Yoon et al., 2005), and may be important for oral squamous epithelial carcinogenesis, as immunohistochemical staining has shown that their expression increases during progression of oral normal mucosa to oral squamous cell carcinoma (Kim et al., 2004b).

Kühne et al., (Kuhne et al., 2007) discloses genetic polymorphisms of the LAT1 and LAT2 genes and relates such polymorphisms to the pharmacokinetics of melphalan. Shennan et al., (Shennan et al., 2008) discloses that inhibiting LAT1 reduces the growth of human breast cancer cells. Nawashiro et al., (Nawashiro et al., 2006) discloses that LAT1 is a potential molecular target in human astrocytic tumors. Yamauchi et al., (Yamauchi et al., 2009) and Kim et al., (Kim et al., 2008) disclose the use of LAT1 inhibitors to block tumor activity of various cancer cells. In the context of the requirement of the 4F2hc chaperone for enabling LAT1 activity, real-time quantitative RT-PCR revealed similar levels of LAT1 and 4F2hc mRNA in KB cells (Yoon et al., 2005). This conflicts with the data from T-24 cells where LAT1 levels were ˜1.5 fold higher than 4F2hc (Kim et al., 2002) and with results in MDA-MB-231 and MCF-7 human breast cancer cells, where LAT1 mRNA was ˜4.3- and ˜4.9-fold higher than 4F2hc (Shennan et al., 2004). Based on the data by (Fuchs et al., 2005), it appears that the overall abundance of 4F2hc mRNA is on par with that of LAT1, but it should be kept in mind that protein and mRNA levels are not always linearly correlated due to the multiple mechanisms of gene expression control. Moreover, cells undoubtedly possess mechanisms that adequately match protein levels of both components, such that 4F2hc is not rate-limiting for vital LAT1-related functions.

When colon cancer RCN-9 cells were injected into the spleen of rats, the size of the resultant metastatic liver tumors was directly correlated to LAT1 expression (Ohkame et al., 2001; Tamai et al., 2001). Thus, it has been proposed that inhibiting LAT1 function could serve as a potential therapeutic for many types of cancers (Kanai et al., 2001). To date, studies targeting LAT1 specifically are scarce. However, in vitro LAT1 antisense expression in non-human hepatic tumor cells resulted in a modest though statistically significant decrease in cell number, viability and S-phase cells over a 5-day period relative to controls despite the absence of a significant decrease in L-type transport over this period (Storey et al., 2005).

Antisense oligonucleotides directed against 4F2hc have been shown to inhibit Na⁺-independent isoleucine transport in C6-BU-1 rat glioma cells (Broer et al., 1997), and leucine uptake in BeWo human cytotrophoblast cells (Kudo et al., 2004), but the effects on cell growth were not reported. An anti-4F2hc antibody inhibited the proliferation of a variety of tumor cell lines (Yagita et al., 1986), but it is possible that these effects were mediated through the collective effects on other 4F2 “light chains” in addition to LAT1, or to non-transport related functions of 4F2hc (Feral et al., 2005). Knockdown of LAT1 in T-24 cells with a LAT1-siRNA against nucleotides 1173-1194 in vitro led to a decrease in L-CSNO uptake (Li et al., 2005), but it is not reported whether cell survival was affected. Thus, mechanistic studies linking the LAT1 “light chain” to cancer growth remain to be reported.

The use of siRNA to inhibit LAT1 gene expression have been disclose by several groups (Kim et al., 2006a; Kim et al., 2006b; Kaneko et al., 2007; Pinho et al., 2007a; Yin et al., 2008; Kuhne et al., 2009; Nicklin et al., 2009; Xia et al., 2010; Liang et al., 2011; Miko et al., 2011; Ohkawa et al., 2011; Denoyer et al., 2012; Hayashi et al., 2012; Dickens et al., 2013; Hayashi et al., 2013; Youland et al., 2013; Gaccioli et al., 2015; Habermeier et al., 2015; Wongthai et al., 2015; Furugen et al., 2016; Polet et al., 2016; Straka et al., 2016; Tomblin et al., 2016; Wei et al., 2016; Xu et al., 2016; Liu et al., 2017).

More recently, LAT1 has been suggested as a marker of cancer prognosis in the types of cancer listed in the following table:

Kidney Renal cell carcinoma (Betsunoh et al., 2013) Urothelial carcinomas (Eltz et al., 2008) Cell carcinoma of the upper urinary (Nakanishi et al., 2007) tract Lung Non-small cell lung cancer (Kaira et al., 2008b; Imai et al., 2009; Kaira et al., 2009c; Kaira et al., 2009d; Kaira et al., 2010b; Kaira et al., 2010a; Kyoichi, 2010; Takeuchi et al., 2010; Kaira et al., 2011b; Kaira et al., 2012a; Chuntao et al., 2015) Pulmonary adenocarcinoma (Kaira et al., 2010b) Squamous cell carcinoma of the lung (Kaira et al., 2009b) Lung cancer (Kaira et al., 2007; Kaira et al., 2011a) Neuroendocrine tumors of the lung (Kaira et al., 2008c; Kyoichi et al., 2008) Malignant pleural mesothelioma (Kaira et al., 2011c) Colon Rectal cancer (Ebara et al., 2010) Breast Breast Cancer (Furuya et al., 2012; Emer et al., 2013; Fukumoto et al., 2013) Pancreas Pancreatic cancer (Kaira et al., 2012b; Yanagisawa et al., 2012; Kaira et al., 2015a) Gastrintestinal Gastric carcinoma (Ichinoe et al., 2011; Ichinoe et al., 2015) Oesophageal cancer (Suzuki et al., 2014) Blood Multiple myeloma (Isoda et al., 2014) Thymic carcinomas (Kaira et al., 2009a) Hepatobilbiar Biliary tract cancer (Kaira et al., 2014; Yanagisawa et al., 2014) Hepatocellular carcinoma (Li et al., 2013; Masashi et al., 2014) Adenoid cystic carcinoma (Kaira et al., 2013) Metastatic Primary metastatsis (Kaira et al., 2008a) Liver Metastasis (Kaoru et al., 2011) Brain Glioma (Keyaerts et al., 2007; Stockhammer et al., 2008; Okubo et al., 2010) Astrocytic tumors (Nawashiro et al., 2006) Head & Neck Oral squamous cell carcinoma (Kim et al., 2004a; Nobusawa et al., 2013) Tongue cancer (Toyoda et al., 2014a) Hypopharyngeal squamous cell (Toyoda et al., 2014b) carcinoma Prostate Prostate cancer (Sakata et al., 2009; Wang et al., 2011; Segawa et al., 2013; Yanagisawa et al., 2015) Uterus Endometrioid adenocarcinoma (Watanabe et al., 2014)

System ASC transport activity is ubiquitous and characterized by its preference for small neutral amino acids including alanine, serine, and cysteine. The system ASC of neutral amino acid transporters (SLC1A4 and SLC1A5) belongs to the solute carrier family-1 (SLC1), which also includes the high-affinity glutamate transporters. Human ATB0 was identified by RT-PCR and enzymatic restriction analysis in the human proximal tubule cell line HKPT and corresponds to rodent ASCT2. The two ASC transporters exhibit distinct substrate selectivity. SLC1A4 encodes the sodium-dependent amino acid transporter ASCT1, which accepts L-alanine, Lserine, L-theonine, and L-cysteine in a stereospecific manner. ASCT2, the second isoform of the ASC transport system, is encoded by SLC1A5. In the kidney and intestine, ASCT2 is present in the brush-border membranes of the proximal tubule cells and enterocytes, respectively. In addition to the typical system ASC substrates, it also accepts L-glutamine and L-asparagine at higher affinity as well as methionine, leucine, and glycine with lower affinity. Both ASCT1 and ASCT2 mediate the sodium-dependent obligatory exchange of substrate amino acids (Pinho et al., 2007b).

More recently, ASCT2 has been suggested as a marker of cancer prognosis in the types of cancer listed in the following table:

Breast Breast Cancer (Betsunoh et al., 2013; Kim et al., 2013) Brain Neuroblastoma (Ren et al., 2015) Colon Rectal cancer (Witte et al., 2002) Gastrintestinal Oesophageal cancer (Honjo et al., 2016) Head & Neck Lacrimal gland adenocarcinoma (Koo et al., 2015) Tongue cancer (Toyoda et al., 2014a) Laryngeal squamous cell carcinoma (Nikkuni et al., 2015) Thyroid medullary carcinoma (Kim et al., 2016) Hepatobilbiar Hepatocellular carcinoma (Ge et al., 2015) Kidney Renal cell carcinoma (Liu et al., 2015) Lung Non-small cell lung cancer (Shimizu et al., 2014) Metastatic Primary metastatsis (Kim et al., 2014) Pancreas Pancreatic cancer (Kaira et al., 2015a; Kaira et al., 2015b) Skin Melanoma (Wang et al., 2014)

ASCT2 is expressed in colorectal adenocarcinomas and patient survival decreased with increased percentage of ASCT2-positive cancer cells. These results indicate that ASCT2 is expressed in a significant number of colorectal adenocarcinomas, and that ASCT2 expression is associated with aggressive biological behavior (Witte et al., 2002). It has been proposed that ASCT2 appears to be required for the glutamine metabolism in both nonmalignant and malignant prostate. However, ASCT2-positive prostate adenocarcinoma seems to be related to a more aggressive biological behavior. ASCT 2 seems to be involved in tumor progression (Li et al., 2003; Wang et al., 2015). ASCT2 expression has a crucial role in the metastasis of pulmonary adecocarccinomas, and is a potential molecular marker for predicting poor prognosis after surgery (Shimizu et al., 2014). ASCT2 expression was also found to play an important role in tumour cell growth, and is a promising pathological marker for predicting a worse outcome in pancreatic cancer (Kaira et al., 2015b; Kyoichi et al., 2015). High ASCT2 expression was also found to be significantly associated with poor prognosis and survival of neuroblastoma patients (Ren et al., 2015). In addition, others have suggested that ASCT2 suppression exerts proapoptotic effects transcending those of glutamine starvation alone (Bryan et al., 2004; Fuchs et al., 2004). The importance of ASCT2 expression in melanoma was confirmed by shRNA knockdown, which inhibited glutamine uptake, mTORC1 signalling and cell proliferation (Wang et al., 2014).

The use of siRNA to inhibit ASCT2 gene expression have been disclose by several groups (Wieland et al., 2005; Nicklin et al., 2009; Okudaira et al., 2011; Barel et al., 2012; Hassanein et al., 2013; Hassanein et al., 2015; Corbet et al., 2016; Straka et al., 2016; Zhou et al., 2016; Lee et al., 2017).

RNA interference (“RNAi”) is a recently discovered mechanism of post-transcriptional gene silencing in which double-stranded RNA corresponding to a gene (or coding region) of interest is introduced into an organism, resulting in degradation of the corresponding mRNA. The phenomenon was originally discovered in Caenorhabditis elegans (Fire et al., 1998).

Unlike antisense technology, the RNAi phenomenon persists for multiple cell divisions before gene expression is regained. The process occurs in at least two steps: an endogenous ribonuclease cleaves the longer dsRNA into shorter, 21- 22- or 23-nucleotide-long RNAs, termed “small interfering RNAs” or siRNAs (Hannon, 2002). The siRNA segments then mediate the degradation of the target m RNA. RNAi has been used for gene function determination in a manner similar to but more efficient than antisense oligonucleotides. By making targeted knockouts at the RNA level by RNAi, rather than at the DNA level using conventional gene knockout technology, a vast number of genes can be assayed quickly and efficiently. RNAi is therefore an extremely powerful, simple method for assaying gene function.

RNAi has been shown to be effective in cultured mammalian cells. In most methods described to date, RNAi is carried out by introducing double-stranded RNA into cells by microinjection or by soaking cultured cells in a solution of double-stranded RNA, as well as transfecting the cells with a plasmid carrying a hairpin-structured siRNA expressing cassette under the control of suitable promoters, such as the U6, H1 or cytomegalovirus (“CMV”) promoter (Elbashir et al., 2001; Harborth et al., 2001; Lee et al., 2001; Brummelkamp et al., 2002; Miyagishi et al., 2002; Paddison et al., 2002; Paul et al., 2002; Sui et al., 2002; Xia et al., 2002; Yu et al., 2002). The gene-specific inhibition of gene expression by double-stranded ribonucleic acid is generally described in U.S. Pat. No. 6,506,559, which is incorporated herein by reference. Exemplary use of siRNA technology is further described in Published U.S. Patent Application No. 2003/01090635 and Published U.S. Patent Application NO. 20040248174, which are incorporated herein by reference. Davis (Davis, 2009) describes the targeted delivery of siRNA to humans using nanoparticle technology.

SUMMARY OF THE INVENTION

An object of the present invention is to use an RNA interference technique to down regulate the expression of the LAT1 and/or ASCT2 genes in order to treat or prevent cancer. Preferred cancers that can be treated or prevented by the present invention include bladder, brain, colon, head and neck, kidney, liver, lung, lymph node, mammary gland, muscle, ovary, pancreas, skin and stomach cancers. The compositions (or molecules) of the invention comprises or consists of short interfering nucleic acid molecules (siNA) and related compounds including, but not limited to, siRNA. The present invention encompasses compositions and methods of use of siNA including, but not limited to short interfering RNA (siRNA), double-stranded RNA (dsRNA), micro-RNA (miRNA), antagomirs and short hairpin RNA (shRNA) capable of mediating RNA interference. In one embodiment, the siNA molecule of the invention can be incorporated into RISC (RNA-induced silencing complex).

A further object of the present invention is to provide a siRNA molecule that efficiently down regulates the expression of the LAT1 gene and/or ASCT2 gene.

Accordingly, in a first aspect, the invention relates to a siNA molecule, wherein said molecule specifically targets at least one sequence selected from SEQ ID NO: 1-SEQ ID NO: 104 or a variant thereof and SEQ ID NO: 209-SEQ ID NO: 297 or a variant thereof. In an alternative embodiment, the invention relates to an siNA molecule wherein said molecule specifically targets at least one sequence complementary to at least one sequence selected from SEQ ID NO: 1-SEQ ID NO: 104 or a variant thereof and SEQ ID NO: 209-SEQ ID NO: 297 or a variant thereof. In one embodiment, the invention relates to an isolated siNA molecule, preferably an isolated siRNA molecule.

In one embodiment, the siNA molecule reduces expression of the (preferably, human) LAT 1 and/or ASCT2 gene when introduced into a cell.

In one embodiment, the siNA molecule specifically targets at least one sequence selected from SEQ ID No 4, 6, 10, 13, 22, 34, 58, 61, 81, 83, 87 and 95 to 104 or a variant thereof. Preferably, the siNA molecule targets a sequence selected from SEQ ID NO 6, 22, 34, 58 and 61 or a variant thereof. Even more preferably, the siNA targets SEQ ID NO: 61 or 58 to a variant thereof. Preferably, the siNA molecule reduces expression of the LAT1 gene when expressed into a cell.

In an alternative embodiment, the siNA molecule specifically targets at least one sequence selected from SEQ ID NO: 209, 216, 225, 226, 228, 235 to 238, 245, 260, 264, 267, 271, 272, 278, 279 and 281 to 297. Preferably, the siNA molecule targets a sequence selected from SEQ ID NO 225, 237, 267 or 278 or a variant thereof. Even more preferably, the siNA targets SEQ ID NO: 267 or 278 or a variant thereof. Preferably the siNA molecule reduces expression of the ASCT2 gene when expressed into a cell.

In a further embodiment, the siNA preferably comprises a double-stranded RNA molecule, whose antisense strand is substantially complementary to any of SEQ ID NO: 1-SEQ ID NO: 104, more preferably SEQ ID No 4, 6, 10, 13, 22, 34, 58, 61, 81, 83, 87 and 95 to 104, even more preferably SEQ ID NO 6, 22, 34, 58 and 61, and most preferably SEQ ID NO: 61 or 58 or any variant thereof, and its sense strand will comprise an RNA sequence complementary to the sense strand, wherein both strands are hybridised by standard base pairing between nucleotides. In a further embodiment, said sense stand comprises or consists of a sequence selected from SEQ ID NO: 105 to 208, preferably SEQ ID NO: 108, 110, 114, 117, 126, 138, 162, 165, 185, 187, 191 and 199 to 208, more preferably SEQ ID NO: 110, 126, 138, 162 and 165 and most preferably SEQ ID NO: 162 or 165 or a variant thereof. The corresponding antisense strands are described in FIGS. 26A-D. Preferably, the siNA molecule reduces expression of the LAT1 gene when expressed into a cell.

In an alternative embodiment, the siNA preferably comprises a double-stranded RNA molecule, whose antisense strand is substantially complementary to any of SEQ ID NO: 209-SEQ ID NO: 297, more preferably SEQ ID NO: 209, 216, 225, 226, 228, 235 to 238, 245, 260, 264, 267, 271, 272, 278, 279 and 281 to 297, even more preferably SEQ ID NO 225, 237, 267 or 278 and most preferably SEQ ID NO: 267 or 278 or any variant thereof, and its sense strand will comprise an RNA sequence complementary to the sense strand, wherein both strands are hybridised by standard base pairing between nucleotides. In a further embodiment, said sense stand comprises or consists of a sequence selected from SEQ ID NO: 298 to 386, preferably, SEQ ID NO: 298, 305, 314, 315, 317, 324-327, 334, 349, 353, 356, 360, 361, 367, 368 and 370 to 386, more preferably SEQ ID NO: 314, 326, 36 and 367 or a variant thereof, and even more preferably SEQ ID NO: 356 or 367 or any variant thereof. The corresponding antisense strands are described in FIG. 27. Preferably, the siNA molecule reduces expression of the ASCT2 gene when expressed into a cell.

Within the meaning of the present invention “substantially complementary” to a target mRNA sequence, may also be understood as “substantially identical” to said target sequence. “Identity” as is known by one of ordinary skill in the art, is the degree of sequence relatedness between nucleotide sequences as determined by matching the order and identity of nucleotides between sequences. In one embodiment the antisense strand of an siRNA having 80%, and between 80% up to 100% complementarity, for example, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 99% complementarity, to the target mRNA sequence are considered substantially complementary and may be used in the present invention. The percentage of complementarity describes the percentage of contiguous nucleotides in a first nucleic acid molecule that can base pair in the Watson-Crick sense with a set of contiguous nucleotides in a second nucleic acid molecule.

A gene is “targeted” by a siNA according to the present invention when, for example, the siNA molecule selectively decreases or inhibits the expression of the gene. The phrase “selectively decrease or inhibit” as used herein encompasses siNAs that affect expression of LAT1 and/or ASCT2. Alternatively, a siNA targets a gene when the siNA hybridizes under stringent conditions to the gene transcript, i.e. its mRNA. Capable of hybridizing “under stringent conditions” means annealing to the target mRNA region, under standard conditions, e.g., high temperature and/or low salt content which tend to disfavor hybridization. A suitable protocol (involving 0.1×SSC, 68° C. for 2 hours) is described in Maniatis, T., et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, 1982, at pages 387-389.

Nucleic acid sequences cited herein are written in a 5′ to 3′ direction unless indicated otherwise. The term “nucleic acid” refers to either DNA or RNA or a modified form thereof comprising the purine or pyrimidine bases present in DNA (adenine “A”, cytosine “C”, guanine “G”, thymine “T”) or in RNA (adenine “A”, cytosine “C”, guanine “G”, uracil “U”). Interfering RNAs provided herein may comprise “T” bases, for example at 3′ ends, even though “T” bases do not naturally occur in RNA. In some cases these bases may appear as “dT” to differentiate deoxyribonucleotides present in a chain of ribonucleotides.

In one embodiment of the invention, the siNA molecule is 40 base pairs or fewer in length. Preferably, the siNA molecule is 19 to 25 base pairs in length. In one embodiment, the siNA comprises or consists of a 21 nucleotide double-stranded region. Preferably, the siNA has a sense and an anti-sense strand. In an alternative embodiment, the siNA molecule comprises or consists of a 19 nucleotide double-stranded region. In one embodiment, the siNA has blunt ends. In an alternative embodiment, the siNA has 5′ and/or 3′ overhangs. Preferably the overhangs are between 1 to 5 nucleotides, more preferably, 2 nucleotide overhangs. The overhangs may be ribonucleic acids, or deoxyribonucleic acids.

In one embodiment, the siNA molecule according to the invention comprises a chemical modification. Preferably, the chemical modification is on the sense strand, the antisense strand or both. Examples of chemical modifications include phosphorothioate internucleotide linkages, 2′-OMethylation, 2′-deoxy-fluoro ribonucleotides, 2′-deoxy ribonucleotides, 5-C methyl nucleotides, inverted deoxybasic residue incorporation or a substitution of uracyl ribose nucleotides with deoxythymidine nucleotides or combinations thereof.

In one embodiment, the 5′ or 3′ overhangs are dinucleotides, preferably thymidine dinucleotide. In a preferred embodiment, the 5′ or 3′ overhangs are deoxythymidines. In one embodiment, the sense strand comprises at least one, preferably two 3′ overhangs. Preferably, said sense strand comprises at least one, preferably two 3′ deoxythymidines. In an alternative embodiment, the antisense strand comprises at least one, preferably two 3′ overhangs. Preferably, said sense strand comprises at least one, preferably two 3′ deoxythymidines. In a further preferred embodiment, both the sense and antisense strands comprise 3′ overhangs as described herein.

In a further embodiment, the siNA molecule preferably comprises a double-stranded RNA molecule, wherein preferably the sense strand and the anti-sense strand are selected from the below or a variant thereof.

Sense strand Anti-sense strand 387  388. This sequence is also referred to herein as SEQ ID NO: 58/387/388. 389 390 This sequence is also referred to herein as SEQ ID NO: 58/389/390 389 412 This sequence is also referred to herein as SEQ ID NO: 58/389/412 391 392 This sequence is also referred to herein as SEQ ID NO: 61/391/392 393 394 This sequence is also referred to herein as SEQ ID NO: 61/393/394 395 396 This sequence is also referred to herein as SEQ ID NO: 61/395/396 397 398 This sequence is also referred to herein as SEQ ID NO: 267/397/398 399 400 This sequence is also referred to herein as SEQ ID NO: 267/399/400 401 402 This sequence is also referred to herein as SEQ ID NO: 267/401/402 403 404 This sequence is also referred to herein as SEQ ID NO: 278/403/404 405 406 This sequence is also referred to herein as SEQ ID NO: 278/405/406 407 408 This sequence is also referred to herein as SEQ ID NO: 278/407/408

By “variant” as used herein is meant a sequence with 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% overall sequence identity to the non-variant nucleic or ribonucleic acid sequence.

By “down-regulating” is meant a decrease in the expression of LAT1 and/or ASCT2 by up to or more than 10%, 15% 20%, 25%, 30%, 35%, 40%, 45% 50%, 55% 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% when compared to the level in a control. Alternatively, the siNA molecule described herein may abolish LAT1 and/or ASCT2 expression. The term “abolish” means that no expression of LAT1 and/or ASCT2 is detectable or that no functional LAT1 and/or ASCT2 protein is produced. For example, a reduction in the expression and/or protein levels of at least LAT1 and/or ASCT2 expression may be a measure of protein and/or nucleic acid levels and can be measured by any technique known to the skilled person, such as, but not limited to, any form of gel electrophoresis or chromatography (e.g. HPLC).

Notably, in some embodiments, the siNA molecule (either the 5′ or 3′ strand or both) may begin with at least one, preferably two alanine nucleotides. Alternatively, if the target sequence starts with one or two alanine sequences, these may not be included (targeted) in the siNA molecule.

In one embodiment, the target sequence may be characterised by at least one, preferably two alanine nucleotides at the 3′ end of the sequence, and/or the target sequence lacks at least one, preferably two alanine nucleotides at the 5′ end of the sequence, and/or the target sequence lacks two consecutive alanine nucleotides within the sequence. In a preferred embodiment, the siNA molecules of the invention are characterised in that they target sequences with the above properties.

In one embodiment a plurality of species of siNA molecule are used, wherein said plurality of siNA molecules are targeted to the same or a different mRNA species.

In one embodiment, the siNA is selected from dsRNA, siRNA or shRNA. Preferably, the siNA is siRNA.

In a further embodiment, the invention relates to a siNA molecule, as herein described for use as a medicament. In one embodiment, the invention relates to a siNA for use in the treatment of a disorder characterised by increased expression levels (compared to the levels in a healthy subject) of LAT1 and/or ASCT2.

In another aspect of the invention, there is provided a siNA molecule, as described herein for use in the treatment of cancer.

In a further aspect, the invention relates to the use of at least one siNA molecule, as described herein in the preparation of a medicament for the treatment of cancer.

In another aspect, the invention relates to a method for the treatment of cancer, the method comprising administering at least one siNA molecule, as described herein, to a patient or subject in need thereof.

In one embodiment, the cancer is selected from bladder, blood, brain, colon, head and neck, kidney, liver, lung, lymph node, mammary gland, muscle, ovary, pancreas, prostate, skin, stomach and uterus cancer.

In another aspect of the invention there is provided a pharmaceutical composition comprising at least one siNA molecule as described herein and a pharmaceutically acceptable carrier.

In a further aspect of the invention there is provided a method, preferably an in vitro method of inhibiting amino acid uptake into a cell, the method comprising administering a siNA as defined herein to a cell. Preferably, the amino acid uptake is sodium-independent leucine uptake. Alternatively, the amino acid uptake is sodium-dependent alanine uptake. In one embodiment, amino acid uptake is inhibited by up to or more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% when compared to the level in a control.

In a further aspect of the invention, there is provided a method of decreasing cell proliferation, the method comprising administering at least on siNA as described herein to a cell. In one embodiment, said decrease in cell proliferation may be up to or more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% when compared to the level in a control.

In a yet further aspect of the invention, there is provided a method of reducing tumour volume, preferably in a patient, the method comprising administering at least one siNA as described herein. In one embodiment, said decrease in tumour volume may be up to or more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% when compared to the level in a control.

In on embodiment, of the above-described methods at least one LAT-1 siNA or at least one ASCT2 siNA is administered. In an alternative embodiment, at least one LAT-1 siNA and at least one ASCT2 siNA is administered

In another embodiment, the invention relates to methods of reducing cancer cell proliferation comprising treating the cells with an siNA of the invention in combination with one or more anti-cancer agents known in the art, preferably wherein the anti-cancer agent comprises an anti-antineoplastic agent, more preferably a cytotoxic antineoplastic agent and most preferably 5-fluoruracil (5-FU), cisplatin (Cisp) and/or oxaliplatin (Oxa).

The invention also relates to methods of treating cancer comprising administrating an siNA of the invention in combination with one or more anti-cancer agents known in the art, preferably to a patient in need thereof, preferably wherein the anti-cancer agent comprises an anti-antineoplastic agent, more preferably a cytotoxic antineoplastic agent and most preferably 5-fluoruracil (5-FU), cisplatin (Cisp) and/or oxaliplatin (Oxa). The invention further relates to pharmaceutical compositions comprising the siNA of the invention and the one or more anti-cancer agent.

In another embodiment the invention relates to methods for increasing the efficacy of an anti-cancer therapy given to a patient comprising administering an siNA of the invention in combination with the therapy. Said increase in efficacy may be up to or more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% when compared to the efficacy of either administration of siNA or the anti-cancer agent alone.

In a preferred embodiment, said siNA targets SEQ ID NO: 58 or SEQ ID NO: 61 (for example, the siNA comprises a sense strand comprising a sequence selected from SEQ ID NO: 162 or 165 respectively) or a variant thereof. In a further alternative embodiment, said siNA comprises a sense strand, wherein the sequence of the sense strand is SEQ ID NO 387 or a variant thereof, and an antisense strand, wherein the sequence of the antisense strand is SEQ ID NO: 388 or a variant thereof. Alternatively, said siNA comprises a sense strand, wherein the sequence of the sense strand is SEQ ID NO 393 or a variant thereof, and an antisense strand, wherein the sequence of the antisense strand is SEQ ID NO: 394 or a variant thereof.

In an alternative embodiment, said siNA targets SEQ ID NO: 267 or 278 or a variant thereof (for example, the siNA comprises a sense strand comprising a sequence selected from SEQ ID NO: 356 or 367). In a further alternative embodiment, said siNA comprises a sense strand, wherein the sequence of the sense strand is SEQ ID NO 399 or a variant thereof, and an antisense strand, wherein the sequence of the antisense strand is SEQ ID NO: 400 or a variant thereof. Alternatively, said siNA comprises a sense strand, wherein the sequence of the sense strand is SEQ ID NO 405 or a variant thereof, and an antisense strand, wherein the sequence of the antisense strand is SEQ ID NO: 406 or a variant thereof.

In one embodiment, the anti-cancer agent is administered prior to, concurrently, or after administration of the siNA.

By “control” is meant herein either a cell or a patient administered no siNA or a cell administered a vehicle, as described herein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method of targeting the LAT1 gene and/or ASCT2 gene by knocking down or inhibiting its expression as a novel strategy for cancer therapy. In particular, and according to a first aspect of the present invention, there is provided the use of a siRNA for inhibiting LAT1 gene and/or ASCT2 gene expression in the manufacture of a medicament for treating or preventing cancer, wherein the siRNA comprises a sense LAT1 or ASCT2 nucleic acid and an antisense LAT1 or ASCT2 nucleic acid. The present invention also provides the use of a vector encoding the siRNA for inhibiting LAT1 and ASCT2 gene expression in the manufacture of a medicament for treating or preventing cancer.

According to a second aspect of the present invention, there is provided a method of treating or preventing cancer comprising administering to an individual an effective amount of a siRNA that inhibits LAT1 and/or ASCT2 gene expression, wherein the siRNA comprises a sense LAT1 or ASCT2 nucleic acid and an antisense LAT1 or ASCT2 nucleic acid. The present invention also provides a method of treating or preventing cancer comprising administering to an individual an effective amount of a vector encoding the siRNA that inhibits LAT1 and ASCT2 gene expression.

Overexpression of the LAT1 transporter, an isoform of system L Na⁺-independent neutral amino acid transporter, is a highly prevalent observation in various forms of cancer. The present invention is based on the surprising discovery that small interfering RNAs (siRNAs) selective for LAT1 are effective for treating cancer. In particular, bladder, blood, brain, colon, head and neck, kidney, liver, lung, lymph node, mammary gland, metastatic, muscle, ovary, pancreas, prostate, skin, stomach and uterus cancer.

The siRNA or vector encoding the siRNA, or the medicament comprising the siRNA or vector encoding the siRNA, may be administered to an individual by enteral administration (e.g., oral, rectal and intranasal), parenteral administration (e.g., intravascular administration, peri- and intra-tissue administration, subcutaneous injection or deposition, subcutaneous infusion intraocular administration and direct administration at or near the site of a tumour).

According to a third aspect of the present invention there is provided an in vitro method of inhibiting the expression of the LAT1 gene and/or ASCT2 gene in a cell comprising contacting the cell with siNA that inhibits LAT1 and/or ASCT2 gene expression as described herein. In one embodiment, said siRNA comprises a sense LAT1 and/or ASCT2 nucleic acid and an anti-sense LAT1 and/or ASCT2 nucleic acid, wherein the sense LAT1 or ASCT2 nucleic acid is substantially identical to a target sequence contained within LAT1 or AST2 mRNA and the anti-sense LAT1 or ASCT2 nucleic acid is complementary to the sense LAT1 or ASCT2 nucleic acid. The present invention also provides an in vitro method of inhibiting the expression of the LAT1 and/or ASCT2 genes in a cell comprising contacting the cell with a vector encoding a siRNA that inhibits LAT1 and/or ASCT2 gene expression, said siRNA comprises a sense LAT1 and/or ASCT2 nucleic acid and an anti-sense LAT1 and/or ASCT2 nucleic acid, wherein the sense LAT1 or ASCT2 nucleic acid is substantially identical to a target sequence contained within LAT1 or ASCT2 mRNA and the anti-sense LAT1 or ASCT2 nucleic acid is complementary to the sense LAT1 or ASCT2 nucleic acid.

Expression of the gene may be inhibited by introduction of a double stranded ribonucleic acid (dsRNA) molecule into the cell in an amount sufficient to inhibit expression of the LAT1 and/or ASCT2 genes.

The siRNAs used in the invention are believed to cause the RNAi-mediated degradation of LAT1 or ASCT2 mRNA so that the protein product of the LAT1 or ASCT2 gene is not produced or is produced in reduced amounts. The siRNAs used in the invention can be used to alter gene expression in a cell in which expression of LAT1 and/or ASCT2 is upregulated, e.g., as a result of malignant transformation of the cells. Binding of the siRNA to a LAT1 or ASCT mRNA transcript in a cell results in a reduction in LAT1 and ASCT2 production by the cell.

The term “siRNA” is used to mean a double stranded RNA molecule which prevents translation of a target mRNA. Standard techniques of introducing siRNA into the cell are used, including those in which DNA is a template from which RNA is transcribed. The siRNA that inhibits LAT1 or ASCT2 gene expression includes a sense LAT1 or ASCT2 nucleic acid sequence and an antisense LAT1 or ASCT2 nucleic acid sequence. The siRNA may be constructed such that a single transcript has both the sense and complementary antisense sequences from the target gene, e.g., in the form of a hairpin.

The siRNA preferably comprises short double-stranded RNA that is targeted to the target mRNA, i.e., LAT1 mRNA or ASCT2 mRNA. The siRNA comprises a sense RNA strand and a complementary antisense RNA strand annealed together by standard Watson-Crick base-pairing interactions (hereinafter “base-paired”). The sense strand comprises a nucleic acid sequence which is substantially identical to a target sequence contained within the LAT1 mRNA or ASCT2 mRNA.

The terms “sense/antisense sequences” and “sense/antisense strands” are used interchangeable herein to refer to the parts of the siRNA of the present invention that are substantially identical (sense) to the target LAT1 and ASCT2 mRNA sequence or substantially complementary (antisense) to the target LAT1 and ASCT2 mRNA sequence.

As used herein, a nucleic acid sequence “substantially identical” to a target sequence contained within the target mRNA is a nucleic acid sequence which is identical to the target sequence, or which differs from the target sequence by one or more nucleotides. Preferably, the substantially identical sequence is identical to the target sequence or differs from the target sequence by one, two or three nucleotides, more preferably by one or two nucleotides and most preferably by only 1 nucleotide. Sense strands which comprise nucleic acid sequences substantially identical to a target sequence are characterized in that siRNA comprising such a sense strand induces RNAi-mediated degradation of mRNA containing the target sequence. For example, an siRNA of the invention can comprise a sense strand comprising a nucleic acid sequence which differs from a target sequence by one, two, three or more nucleotides, as long as RNAi-mediated degradation of the target mRNA is induced by the siRNA.

The sense and antisense strands of the siRNA can comprise two complementary, single-stranded RNA molecules or can comprise a single molecule in which two complementary portions are base-paired and are covalently linked by a single-stranded “hairpin” area. That is, the sense region and antisense region can be covalently connected via a linker molecule. The linker molecule can be a polynucleotide or non-nucleotide linker. The siRNA can also contain alterations, substitutions or modifications of one or more ribonucleotide bases. For example, the present siRNA can be altered, substituted or modified to contain one or more, preferably 0, 1, 2 or 3, deoxyribonucleotide bases. Preferably, the siRNA does not contain any deoxyribonucleotide bases.

The siRNA can comprise partially purified RNA, substantially pure RNA, synthetic RNA, or recombinantly produced RNA, as well as altered RNA that differs from naturally-occurring RNA by the addition, deletion, substitution and/or alteration of one or more nucleotides. Such alterations can include addition of non-nucleotide material, such as to the end(s) of the siRNA or to one or more internal nucleotides of the siRNA; modifications that make the siRNA resistant to nuclease digestion (e.g., the use of 2′-substituted ribonucleotides or modifications to the sugar-phosphate backbone); or the substitution of one or more, preferably 0, 1, 2 or 3, nucleotides in the siRNA with deoxyribonucleotides.

Degradation can be delayed or avoided by a wide variety of chemical modifications that include alterations in the nucleobases, sugars and the phosphate ester backbone of the siRNAs. All of these chemically modified siRNAs are still able to induce siRNA-mediated gene silencing provided that the modifications were absent in specific regions of the siRNA and included to a limited extent. In general, backbone modifications cause a small loss in binding affinity, but offer nuclease resistance. Phosphorothioate (PS)- or boranophosphate (BS)-modified siRNAs have substantial nuclease resistance. Silencing by siRNA duplexes is also compatible with some types of 2′-sugar modifications: 2′-H, 2′-O-methyl, 2′-O-methoxyethyl, 2′-fluoro (2′-F), locked nucleic acid (LNA) and ethylene-bridge nucleic acid (ENA). Suitable chemical modifications are well known to those skilled in the art.

The siRNA used in the present invention is a double-stranded molecule comprising a sense strand and an antisense strand, wherein the sense strand comprises or consists of a ribonucleotide sequence corresponding to a LAT1 or ASCT2 target sequence, and wherein the antisense strand comprises a ribonucleotide sequence which is complementary to said sense strand, wherein said sense strand and said antisense strand hybridize to each other to form said double-stranded molecule, and wherein said double-stranded molecule, when introduced into a cell expressing the LAT1 and ASCT2 genes, inhibits expression of said genes. As indicated further below, said LAT1 target sequence preferably comprises at least about 10 contiguous, more preferably 15 to 21, and most preferably about 19 to 21 contiguous nucleotides selected from the group consisting of from SEQ ID NOS 4, 6, 10, 13, 22, 34, 58, 61, 81, 83, 87, and 95 to 104. As indicated further below, said ASCT2 target sequence preferably comprises at least about 10 contiguous, more preferably 15 to 21, and most preferably about 19 to 21 contiguous nucleotides selected from the group consisting of from SEQ ID NOS 209, 216, 225, 226, 228, 235-238, 245, 260, 264, 267, 271, 272, 278, 279, 281 to 297.

In one embodiment of the present invention, said sense strand and antisense strand of the siRNA molecule are covalently connected via a linker molecule. Said linker molecule may be a polynucleotide linker or a non-nucleotide linker. Preferably the linker is a loop sequence. The loop sequence is preferably 3 to 23 nucleotide in length. Suitable loop sequences are described at www.ambion.com/techlib/tb/tb_506.html and (Jacque et al., 2002). Preferred loop sequences include:

-   -   AUG: (Sui et al., 2002).     -   CCC, CCACC or CCACACC: (Paul et al., 2002).     -   UUCG: (Lee et al., 2002).     -   CTCGAG or AAGCUU: (Biology, 2003).     -   UUCAAGAGA: (Yu et al., 2002).

The loop sequence can be selected from group consisting of AUG, CCC, UUCG, CCACC, CTCGAG, AAGCUU, CCACACC, and UUCAAGAGA. Preferably the loop sequence is UUCAAGAGA (“ttcaagaga” in DNA).

The siRNA used in the present invention can be obtained using a number of techniques known to those of skill in the art. For example, the siRNA can be chemically synthesized or recombinantly produced using methods known in the art, such as the Drosophila in vitro system described in U.S. published application 2002/0086356, the entire disclosure of which is herein incorporated by reference. The siRNA may be chemically synthesized using appropriately protected ribonucleoside phosphoramidites and a conventional DNA/RNA synthesizer. The siRNA can be synthesized as two separate, complementary RNA molecules, or as a single RNA molecule with two complementary regions. Commercial suppliers of synthetic RNA molecules or synthesis reagents include Biospring (Frankfurt, Germany), Proligo (Hamburg, Germany), Dharmacon Research (Lafayette, Colo., USA), Thermo Fisher Scientific (Waltham, Mass. USA), Glen Research (Sterling, Va., USA), ChemGenes (Ashland, Mass., USA) and Sigma-Aldrich (St. Louis, Mo. USA).

The siRNA can also be expressed from recombinant circular or linear DNA vectors using any suitable promoter. Suitable promoters for expressing siRNA from a vector include, for example, the U6 or H1 RNA pol III promoter sequences and the cytomegalovirus promoter. Selection of other suitable promoters is within the skill in the art. The vector can also comprise inducible or regulatable promoters for expression of the siRNA in a particular tissue or in a particular intracellular environment.

The siRNA expressed from a vector can either be isolated from cultured cell expression systems by standard techniques, or can be expressed intracellularly. The vector can be used to deliver the siRNA to cells in vivo, e.g., by intracellularly expressing the siRNA in vivo. siRNA can be expressed from a vector either as two separate, complementary RNA molecules, or as a single RNA molecule with two complementary regions. Selection of vectors suitable for expressing the siRNA, methods for inserting nucleic acid sequences for expressing the siRNA into the vector, and methods of delivering the vector to the cells of interest are well known to those skilled in the art.

The siRNA can also be expressed from a vector intracellularly in vivo. As used herein, the term “vector” means any nucleic acid- and/or viral-based technique used to deliver a desired nucleic acid. Any vector capable of accepting the coding sequences for the siRNA molecule(s) to be expressed can be used, including plasmids, cosmids, naked DNA, optionally condensed with a condensing agent, and viral vectors. Suitable viral vectors include vectors derived from adenovirus (AV); adeno-associated virus (AAV); retroviruses (e.g., lentiviruses (LV), Rhabdoviruses, murine leukemia virus); herpes virus, and the like. The tropism of viral vectors can be modified by pseudotyping the vectors with envelope proteins or other surface antigens from other viruses, or by substituting different viral capsid proteins, as appropriate. When the vector is a lentiviral vector it is preferably pseudotyped with surface proteins from vesicular stomatitis virus, rabies virus, Ebola virus or Mokola virus.

Vectors are produced for example by cloning a LAT1 or ASCT2 target sequence into an expression vector so that operatively-linked regulatory sequences flank the LAT1 or ASCT2 sequence in a manner that allows for expression (by transcription of the DNA molecule) of both strands (Lee et al., 2002). An RNA molecule that is antisense to LAT1 mRNA or ASCT2 mRNA is transcribed by a first promoter (e.g., a promoter sequence 3′ of the cloned DNA) and an RNA molecule that is the sense strand for the LAT1 mRNA or the ASCT2 mRNA is transcribed by a second promoter (e. g., a promoter sequence 5′ of the cloned DNA). The sense and antisense strands hybridize in vivo to generate siRNA constructs for silencing of the LAT1 gene or ASCT2 gene. Alternatively, two vectors are utilized to create the sense and anti-sense strands of a siRNA construct. Cloned LAT1 or ASCT2 can encode a construct having secondary structure, e. g., hairpins, wherein a single transcript has both the sense and complementary antisense sequences from the target gene. Such a transcript encoding a construct having secondary structure, will preferably comprises a single-stranded ribonucleotide sequence (loop sequence) linking said sense strand and said antisense strand.

The siRNA is preferably isolated. As used herein, “isolated” means synthetic, or altered or removed from the natural state through human intervention. For example, a siRNA naturally present in a living animal is not “isolated,” but a synthetic siRNA, or a siRNA partially or completely separated from the coexisting materials of its natural state is “isolated.” An isolated siRNA can exist in substantially purified form, or can exist in a non-native environment such as, for example, a cell into which the siRNA has been delivered. By way of example, siRNA which are produced inside a cell by natural processes, but which are produced from an “isolated” precursor molecule, are themselves “isolated” molecules. Thus, an isolated dsRNA can be introduced into a target cell, where it is processed by the Dicer protein (or its equivalent) into isolated siRNA.

As used herein, “inhibit” means that the activity of the LAT1 or ASCT2 gene expression product or level of the LAT1 or ASCT2 gene expression product is reduced below that observed in the absence of the siRNA molecule of the invention. The inhibition with a siRNA molecule preferably is significantly below that level observed in the presence of an inactive or attenuated molecule that is unable to mediate an RNAi response. Inhibition of gene expression with the siRNA molecule is preferably significantly greater in the presence of the siRNA molecule than in its absence. Preferably, the siRNA inhibits the level of LAT1 or ASCT2 gene expression by at least 10%, more preferably at least 50% and most preferably at least 75%.

Preferably the siRNA molecule inhibits LAT1 or ASCT2 gene expression so that growth of the cell containing the LAT1 or ASCT2 gene is inhibited. By inhibiting cell growth is meant that the treated cell proliferates at a lower rate or has decreased viability than an untreated cell. Cell growth is measured by proliferation assays known in the art.

As used herein, an “isolated nucleic acid” is a nucleic acid removed from its original environment (e. g., the natural environment if naturally occurring) and thus, synthetically altered from its natural state. In the present invention, isolated nucleic acid includes DNA, RNA, and derivatives thereof. When the isolated nucleic acid is RNA or derivatives thereof, base “t” should be replaced with “u” in the nucleotide sequences.

As used herein, the term “complementary” refers to Watson-Crick or Hoogsteen base pairing between nucleotides units of a polynucleotide, and the term “binding” means the physical or chemical interaction between two polypeptides or compounds or associated polypeptides or compounds or combinations thereof.

As used herein, the phrase “highly conserved sequence region” means a nucleotide sequence of one or more regions in a target gene does not vary significantly from one generation to the other or from one biological system to the other.

As used herein, the term “complementarity” or “complementary” means that a nucleic acid can form hydrogen bond(s) with another nucleic acid sequence by either traditional Watson-Crick or other non-traditional types of interaction. In reference to the present invention, the binding free energy for a siRNA molecule with its complementary sequence is sufficient to allow the relevant function of the nucleic acid to proceed, e.g., RNAi activity. For example, the degree of complementarity between the sense and antisense strand of the siRNA molecule can be the same or different from the degree of complementarity between the antisense strand of the siRNA and the target RNA sequence.

A percent complementarity indicates the percentage of contiguous residues in a nucleic acid molecule that can form hydrogen bonds (e.g., Watson-Crick base pairing) with a second nucleic acid sequence (e.g., 5, 6, 7, 8, 9, 10 out of 10 being 50%, 60%, 70%, 80%, 90%, and 100% complementary). “Perfectly complementary” means that all the contiguous residues of a nucleic acid sequence will hydrogen bond with the same number of contiguous residues in a second nucleic acid sequence. Preferably the term “complementarity” or “complementary” means that at least 90%, more preferably at least 95% and most preferably 100% of residues in a first nucleic acid sense can form hydrogen binds with a second nucleic acid sequence.

Complementary nucleic acid sequences hybridize under appropriate conditions to form stable duplexes containing few (one or two) or no mismatches. Furthermore, the sense strand and antisense strand of the siRNA can form a double stranded nucleotide or hairpin loop structure by the hybridization. In a preferred embodiment, such duplexes contain no more than 1 mismatch for every 10 matches. In an especially preferred embodiment, the sense and antisense strands of the duplex are fully complementary, i.e., the duplexes contain no mismatches.

As used herein, the term “cell” is defined using its usual biological sense. The cell can be present in an organism, e.g., mammals such as humans, cows, sheep, apes, monkeys, swine, dogs, and cats. The cell can be eukaryotic (e.g., a mammalian cell). The cell can be of somatic or germ line origin, totipotent or pluripotent, dividing or non-dividing. The cell can also be derived from or can comprise a gamete or embryo, a stem cell, or a fully differentiated cell. Preferably the cell is a bladder, brain, colon, head and neck, kidney, liver, lung, lymph node, mammary gland, muscle, ovary, pancreas, skin or stomach cancer cell.

As used herein, the term “RNA” means a molecule comprising at least one ribonucleotide residue. By “ribonucleotide” is meant a nucleotide with a hydroxyl group at the 2′ position of a beta-D-ribo-furanose moiety. The term includes double stranded RNA, single stranded RNA, isolated RNA such as partially purified RNA, essentially pure RNA, synthetic RNA, recombinantly produced RNA, as well as altered RNA that differs from naturally occurring RNA by the addition, deletion, substitution and/or alteration of one or more nucleotides. Such alterations can include addition of non-nucleotide material, such as to the end(s) of the siRNA or internally, for example at one or more nucleotides of the RNA. Nucleotides in the RNA molecules of the instant invention can also comprise non-standard nucleotides, such as non-naturally occurring nucleotides or chemically synthesized nucleotides or deoxynucleotides. These altered RNAs can be referred to as analogues of naturally-occurring RNA. Preferably the term “RNA” consists of ribonucleotide residues only.

As used herein, the term“organism” refers to any living entity comprised of at least one cell. A living organism can be as simple as, for example, a single eukaryotic cell or as complex as a mammal, including a human being.

As used herein, the term “subject” means an organism, which is a donor or recipient of explanted cells or the cells themselves. “Subject” also refers to an organism to which the nucleic acid molecules of the invention can be administered. The subject is preferably a mammal, e.g., a human, non-human primate, mouse, rat, dog, cat, horse, or cow. Most preferably the subject is a human.

As used herein, the term “biological sample” refers to any sample containing polynucleotides. The sample may be a tissue or cell sample, or a body fluid containing polynucleotides (e.g., blood, mucus, lymphatic fluid, synovial fluid, cerebrospinal fluid, saliva, amniotic fluid, amniotic cord blood, urine, vaginal fluid and semen). The sample may be a homogenate, lysate, extract, cell culture or tissue culture prepared from a whole organism or a subset of its cells, tissues or component parts, or a fraction or portion thereof. Lastly, the sample may be a medium, such as a nutrient broth or gel in which an organism, or cells of an organism, have been propagated, wherein the sample contains polynucleotides.

The invention relates to methods of inhibiting LAT1 and/or ACST2 gene expression which causes the inhibition of cancer cell growth. In particular, the invention provides a method for inhibiting the growth of a cancerous cell population comprising applying the LAT1 and/or ASCT2 siRNA to said cancerous cell population. Cancer cell growth is inhibited by contacting a cell with a composition of a LAT1 and/or ASCT2 siRNA. LAT1 and ASCT2 are amino acid transporter proteins that are overexpressed in tumors such as bladder, brain, colon, head and neck, kidney, liver, lung, lymph node, mammary gland, muscle, ovary, pancreas, skin and stomach cancer. Growth of the cell expressing LAT1 or ASCT2 can be inhibited by a LAT1 or ASCT2 siRNA. The cell may be further contacted with a transfection-enhancing agent to enhance delivery of the siRNA or siRNA encoding vector to the cell. Depending on the specific method of the present invention, the cell may be provided in vitro, in vivo or ex vivo.

Sequence information regarding the human LAT1 gene (GenBank accession NM_003486) was extracted from the NCBI Entrez nucleotide database. Up to 104 mRNA segments were identified. Sequence information regarding the human ASCT2 gene (GenBank accession NM_001145144) was extracted from the NCBI Entrez nucleotide database. Up to 89 mRNA segments were identified. Methods for designing double stranded RNA having the ability to inhibit gene expression in a target cell are known. See for example, U.S. Pat. No. 6,506,559, and Elbashir et al., 2001, herein incorporated by reference in its entirety.

Selection of siRNA target sites can be performed as follows

-   -   1. Beginning with the ATG start codon of the transcript, scan         downstream for AA dinucleotide sequences. Record the occurrence         of each AA and the 3′ adjacent 19 nucleotides as potential siRNA         target sites. Tuschal et al. recommend against designing siRNA         to the 5′ and 3′ untranslated regions (UTRs) and regions near         the start codon (within 75 bases) as these may be richer in         regulatory protein binding sites. UTR-binding proteins and/or         translation initiation complexes may interfere with binding of         the siRNA endonuclease complex.     -   2. Compare the potential target sites to the appropriate genome         database (human, mouse, rat, etc.) and eliminate from         consideration any target sequences with significant homology to         other coding sequences. We suggest using BLAST, which can be         found on the NCBI server at: www.ncbi.nlm.nih.gov/BLAST/     -   3. Select qualifying target sequences (i.e., sequences having         over 55% GC content) for synthesis.

In one aspect of the invention, the length of the sense nucleic acid is at least 10 nucleotides and may be as long as the naturally-occurring LAT1 transcript. Preferably, the sense nucleic acid is less than 75, 50, or 25 nucleotides in length. It is further preferred that the sense nucleic acid comprises at least 19 nucleotides. Most preferably, the sense nucleic acid is 19-25 nucleotides in length. Examples of LAT1 siRNA sense nucleic acids of the present invention which inhibit LAT1 expression in mammalian cells include oligonucleotides comprising any one of the following target sequences of the LAT1 gene: nucleotides 145-165 (SEQ ID NO: 4), 217-237 (SEQ ID NO: 6), 466-486 (SEQ ID NO: 10), 628-648 (SEQ ID NO: 13), 796-816 (SEQ ID NO: 22), 1243-1263 (SEQ ID NO: 34), 525-545 (SEQ ID NO: 58), 624-644 (SEQ ID NO: 61), 1245-1265 (SEQ ID NO: 81), 1316-1336 (SEQ ID NO: 83), 1410-1430 (SEQ ID NO: 87), 147-165 (SEQ ID NO: 95), 219-237 (SEQ ID NO: 96), 468-486 (SEQ ID NO: 97), 630-648 (SEQ ID NO: 98), 798-816 (SEQ ID NO: 99), 1247-1263 (SEQ ID NO: 100), 527-545 (SEQ ID NO: 101), 1247-1265 (SEQ ID NO: 102), 1318-1336 (SEQ ID NO: 103), 1412-1430 (SEQ ID NO: 104).

One hundred and four sequences, which set forth the sequence for one strand of the double stranded is RNA, were generated for LAT-1. These included the following nucleotide sequences:

SEQ ID No 1 AAGCGGCGCGCGCTAGCGGCG SEQ ID No 2 AAGGAAGAGGCGCGGGAGAAG SEQ ID No 3 AAGAGGCGCGGGAGAAGATGC SEQ ID No 4 AAGATGCTGGCCGCCAAGAGC SEQ ID No 5 AAGAGCGCGGACGGCTCGGCG SEQ ID No 6 AACATCACGCTGCTCAACGGC SEQ ID No 7 AAGGAGGCAGGCTCGCCGGGG SEQ ID No 8 AAATCGGGCGGCGACTACGCC SEQ ID No 9 AATCGGGCGGCGACTACGCCT SEQ ID No 10 AAGCTCTGGATCGAGCTGCTC SEQ ID No 11 AAGCCGCTCTTCCCCACCTGC SEQ ID No 12 AAGCTCGTGGCCTGCCTCTGC SEQ ID No 13 AACTGCTACAGCGTGAAGGCC SEQ ID No 14 AAGGCCGCCACCCGGGTCCAG SEQ ID No 15 AAGCTCCTGGCCCTGGCCCTG SEQ ID No 16 AAGGGTGATGTGTCCAATCTA SEQ ID No 17 AATCTAGATCCCAACTTCTCA SEQ ID No 18 AACTTCTCATTTGAAGGCACC SEQ ID No 19 AAGGCACCAAACTGGATGTGG SEQ ID No 20 AAACTGGATGTGGGGAACATT SEQ ID No 21 AACTGGATGTGGGGAACATTG SEQ ID No 22 AACATTGTGCTGGCATTATAC SEQ ID No 23 AATTACTTGAATTTCGTCACA SEQ ID No 24 AATTTCGTCACAGAGGAAATG SEQ ID No 25 AAATGATCAACCCCTACAGAA SEQ ID No 26 AATGATCAACCCCTACAGAAA SEQ ID No 27 AACCCCTACAGAAACCTGCCC SEQ ID No 28 AAACCTGCCCCTGGCCATCAT SEQ ID No 29 AACCTGCCCCTGGCCATCATC SEQ ID No 30 AACCTGGCCTACTTCACCACC SEQ ID No 31 AACTATCACCTGGGCGTCATG SEQ ID No 32 AATGGGTCCCTGTTCACATCC SEQ ID No 33 AAGGCCACCTGCCCTCCATCC SEQ ID No 34 AAGGACATCTTCTCCGTCATC SEQ ID No 35 AACTTCTTCAGCTTCTTCAAC SEQ ID No 36 AACTGGCTCTGCGTGGCCCTG SEQ ID No 37 AAAGCCTGAGCTTGAGCGGCC SEQ ID No 38 AAGCCTGAGCTTGAGCGGCCC SEQ ID No 39 AAGGTGAACCTGGCCCTGCCT SEQ ID No 40 AACCTGGCCCTGCCTGTGTTC SEQ ID No 41 AAGACACCCGTGGAGTGTGGC SEQ ID No 42 AAAAACAAGCCCAAGTGGCTC SEQ ID No 43 AAACAAGCCCAAGTGGCTCCT SEQ ID No 44 AACAAGCCCAAGTGGCTCCTC SEQ ID No 45 AAGCCCAAGTGGCTCCTCCAG SEQ ID No 46 AAGTGGCTCCTCCAGGGCATC SEQ ID No 47 AAGCTCATGCAGGTGGTCCCC SEQ ID No 48 GGCGCCGGCGGCCGAGGAGAA SEQ ID No 49 CCGGCGGCCGAGGAGAAGGAA SEQ ID No 50 GGAGAAGATGCTGGCCGCCAA SEQ ID No 51 GAAGGAAGAGGCGCGGGAGAA SEQ ID No 52 GGAGAAGATGCTGGCCGCCAA SEQ ID No 53 GGGCGTGACCCTGCAGCGGAA SEQ ID No 54 GACGCCCACGGGCGTGCTCAA SEQ ID No 55 GCTCGGCACCACCATCTCCAA SEQ ID No 56 CTCGGCACCACCATCTCCAAA SEQ ID No 57 CTCGCTGCCCGCCTTCCTCAA SEQ ID No 58 CTTCGCCACCTACCTGCTCAA SEQ ID No 59 GGTGCCCGAGGAGGCAGCCAA SEQ ID No 60 GCTGCTGCTCACGGCCGTGAA SEQ ID No 61 CGTGAACTGCTACAGCGTGAA SEQ ID No 62 GGATGCCTTTGCCGCCGCCAA SEQ ID No 63 GGGCTTCGTCCAGATCGGGAA SEQ ID No 64 CGGGAAGGGTGATGTGTCCAA SEQ ID No 65 TGTGTCCAATCTAGATCCCAA SEQ ID No 66 GATCCCAACTTCTCATTTGAA SEQ ID No 67 CTTCTCATTTGAAGGCACCAA SEQ ID No 68 TTCTCATTTGAAGGCACCAAA SEQ ID No 69 ACCAAACTGGATGTGGGGAA SEQ ID No 70 CTTTGCCTATGGAGGATGGAA SEQ ID No 71 TGGAGGATGGAATTACTTGAA SEQ ID No 72 TGAATTTCGTCACAGAGGAAA SEQ ID No 73 CGTCACAGAGGAAATGATCAA SEQ ID No 74 AAATGATCAACCCCTACAGAA SEQ ID No 75 AATGATCAACCCCTACAGAAA SEQ ID No 76 GCTGGTGTACGTGCTGACCAA SEQ ID No 77 CGTGGCCGTGGACTTCGGGAA SEQ ID No 78 GTCCTGCTTCGGCTCCGTCAA SEQ ID No 79 TTCTTCGTGGGGTCCCGGGAA SEQ ID No 80 GCTGCTCTACGCCTTCTCCAA SEQ ID No 81 GGACATCTTCTCCGTCATCAA SEQ ID No 82 CAACTTCTTCAGCTTCTTCAA SEQ ID No 83 TGATCTGGCTGCGCCACAGAA SEQ ID No 84 GATCTGGCTGCGCCACAGAAA SEQ ID No 85 TGAGCTTGAGCGGCCCATCAA SEQ ID No 86 TGAGCGGCCCATCAAGGTGAA SEQ ID No 87 GATCGCCGTCTCCTTCTGGAA SEQ ID No 88 CTTCTTCGGGGTCTGGTGGAA SEQ ID No 89 TTCTTCGGGGTCTGGTGGAAA SEQ ID No 90 TCTTCGGGGTCTGGTGGAAAA SEQ ID No 91 CTTCGGGGTCTGGTGGAAAAA SEQ ID No 92 CGGGGTCTGGTGGAAAAACAA SEQ ID No 93 CTGGTGGAAAAACAAGCCCAA SEQ ID No 94 CACGACCGTCCTGTGTCAGAA SEQ ID No 95 AAGATGCTGGCCGCCAAGAGC SEQ ID No 96 AACATCACGCTGCTCAACGGC SEQ ID No 97 AAGCTCTGGATCGAGCTGCTC SEQ ID No 98 AACTGCTACAGCGTGAAGGCC SEQ ID No 99 AACATTGTGCTGGCATTATAC SEQ ID No 100 AAGGACATCTTCTCCGTCATC SEQ ID No 101 CTTCGCCACCTACCTGCTCAA SEQ ID No 102 GGACATCTTCTCCGTCATCAA SEQ ID No 103 TGATCTGGCTGCGCCACAGAA SEQ ID No 104 GATCGCCGTCTCCTTCTGGAA

The LAT1 gene specificity was confirmed by searching NCBI BlastN database. The siRNAs were chemically synthesized.

All of the forty-two purified siRNA duplexes were complexed with lipofectamine and added to the cells for 12 h in serum-free medium. Thereafter, cells were cultured for 72-96 h in serum-supplemented medium, which was replaced by serum-free medium 24 h before the experiments. A scrambled negative siRNA duplex was used as control.

The LAT1-siRNA is directed to a single target LAT1 gene sequence. Alternatively, the siRNA is directed to multiple target LAT1 gene sequences. For example, the composition contains LAT1-siRNA directed to two, three, four, five or more LAT1 target sequences. By LAT1 target sequence is meant a nucleotide sequence that is identical to a portion of the LAT1 gene. The target sequence can include the 5′ untranslated (UT) region, the open reading frame (ORF) or the 3′ untranslated region of the human LAT1 gene. Alternatively, the siRNA is a nucleic acid sequence complementary to an upstream or downstream modulator of LAT1 gene expression. Examples of upstream and downstream modulators include, a transcription factor that binds the LAT1 gene promoter, a kinase or phosphatase that interacts with the LAT1 polypeptide, a LAT1 promoter or enhance.

LAT1-siRNA which hybridize to target mRNA decrease or inhibit production of the LAT1 polypeptide product encoded by the LAT1 gene by associating with the normally single-stranded mRNA transcript, thereby interfering with translation and thus, expression of the protein. Exemplary nucleic acid sequence for the production of LAT1-siRNA include the sequences of nucleotides 145-165 (SEQ ID NO: 4), 217-237 (SEQ ID NO: 6), 466-486 (SEQ ID NO: 10), 628-648 (SEQ ID NO: 13), 796-816 (SEQ ID NO: 22), 1243-1263 (SEQ ID NO: 34), 525-545 (SEQ ID NO: 58), 624-644 (SEQ ID NO: 61), 1245-1265 (SEQ ID NO: 81), 1316-1336 (SEQ ID NO: 83), 1410-1430 (SEQ ID NO: 87), 147-165 (SEQ ID NO: 95), 219-237 (SEQ ID NO: 96), 468-486 (SEQ ID NO: 97), 630-648 (SEQ ID NO: 98), 798-816 (SEQ ID NO: 99), 1247-1263 (SEQ ID NO: 100), 527-545 (SEQ ID NO: 101), 1247-1265 (SEQ ID NO: 102), 1318-1336 (SEQ ID NO: 103), 1412-1430 (SEQ ID NO: 104) as the target sequence. In a further embodiment, in order to enhance the inhibition activity of the siRNA, nucleotide “u” can be added to 3′ end of the antisense strand of the target sequence. Preferably at least 2, more preferably 2 to 10, and most preferably 2 to 5 u's are added. The added u's form single strand at the 3′ end of the antisense strand of the siRNA.

The LAT1-siRNA can be directly introduced into the cells in a form that is capable of binding to the mRNA transcripts. Alternatively, a vector encoding the LAT1-siRNA can be introduced into the cells.

A loop sequence consisting of an arbitrary nucleotide sequence can be located between the sense and antisense sequence in order to form a hairpin loop structure. Thus, the present invention also provides siRNA having the general formula 5′-[A]-[B]-[A′]-3′, wherein [A] is a ribonucleotide sequence corresponding to a target sequence of the LAT1 gene. Preferably [A] is a sequence selected from the group consisting of nucleotides 145-165 (SEQ ID NO: 4), 217-237 (SEQ ID NO: 6), 466-486 (SEQ ID NO: 10), 628-648 (SEQ ID NO: 13), 796-816 (SEQ ID NO: 22), 1243-1263 (SEQ ID NO: 34), 525-545 (SEQ ID NO: 58), 624-644 (SEQ ID NO: 61), 1245-1265 (SEQ ID NO: 81), 1316-1336 (SEQ ID NO: 83), 1410-1430 (SEQ ID NO: 87), 147-165 (SEQ ID NO: 95), 219-237 (SEQ ID NO: 96), 468-486 (SEQ ID NO: 97), 630-648 (SEQ ID NO: 98), 798-816 (SEQ ID NO: 99), 1247-1263 (SEQ ID NO: 100), 527-545 (SEQ ID NO: 101), 1247-1265 (SEQ ID NO: 102), 1318-1336 (SEQ ID NO: 103), 1412-1430 (SEQ ID NO: 104); [B] is a ribonucleotide sequence consisting of 3 to 23 nucleotides; and [A′] is a ribonucleotide sequence consisting of the complementary sequence of [A]. The region [A] hybridizes to [A′], and then a loop consisting of region [B] is formed. The loop sequence may be preferably 3 to 23 nucleotide in length. Suitable loop sequences are described at www.ambion.com/techlib/tb/tb_506.html. Furthermore, loop sequence consisting of 23 nucleotides also provides active siRNA (Jacque et al., 2002). Preferred loop sequences included:

-   -   AUG: (Sui et al., 2002).     -   CCC, CCACC or CCACACC: (Paul et al., 2002).     -   UUCG: (Lee et al., 2002).     -   CTCGAG or AAGCUU: (Biology, 2003).     -   UUCAAGAGA: (Yu et al., 2002).

The loop sequence can be selected from group consisting of AUG, CCC, UUCG, CCACC, CTCGAG, AAGCUU, CCACACC, and UUCAAGAGA. Preferably the loop sequence is UUCAAGAGA (“ttcaagaga” in DNA).

In a further aspect of the invention, the length of the sense nucleic acid is at least 10 nucleotides and may be as long as the naturally-occurring ASCT2 transcript. Preferably, the sense nucleic acid is less than 75, 50, or 25 nucleotides in length. It is further preferred that the sense nucleic acid comprises at least 19 nucleotides. Most preferably, the sense nucleic acid is 19-25 nucleotides in length. Examples of ASCT2 siRNA sense nucleic acids of the present invention which inhibit ASCT2 expression in mammalian cells include oligonucleotides comprising any one of the following target sequences of the ASCT2 gene: nucleotides 300-320 (SEQ ID NO: 209), 452-472 (SEQ ID NO: 216), 773-793 (SEQ ID NO: 225), 776-796 (SEQ ID NO: 226), 830-850 (SEQ ID NO: 228), 1122-1142 (SEQ ID NO: 235), 1123-1143 (SEQ ID NO: 236), 1124-1144 (SEQ ID NO: 237), 1150-1170 (SEQ ID NO: 238), 769-789 (SEQ ID NO: 260), 994-1014 (SEQ ID NO: 264), 1066-1086 (SEQ ID NO: 267), 1131-1151 (SEQ ID NO: 271), 1154-1174 (SEQ ID NO: 272), 1264-1284 (SEQ ID NO: 278), 1268-1288 (SEQ ID NO: 279), 302-320 (SEQ ID NO: 281), 454-472 (SEQ ID NO: 282), 775-793 (SEQ ID NO: 283), 778-796 (SEQ ID NO: 284), 832-850 (SEQ ID NO: 285), 1124-1142 (SEQ ID NO: 286), 1125-1143 (SEQ ID NO: 287), 1126-1144 (SEQ ID NO: 288), 1152-1170 (SEQ ID NO: 289), 771-789 (SEQ ID NO: 291), 996-1014 (SEQ ID NO: 292), 1068-1086 (SEQ ID NO: 293), 1133-1151 (SEQ ID NO: 294), 1156-1174 (SEQ ID NO: 295), 1266-1284 (SEQ ID NO: 296), 1270-1288 (SEQ ID NO: 297).

Eighty-nine sequences, which set forth the sequence for one strand of the double stranded is RNA, were generated for ASCT2. These included the following nucleotide sequences:

SEQ ID No 209 AAGAGAGGAATATCACCGGAA SEQ ID No 210 AATATCACCGGAACCAGGGTG SEQ ID No 211 AACCAGGGTGAAGGTGCCCGT SEQ ID No 212 AAGGTGCCCGTGGGGCAGGAG SEQ ID No 213 AACATCCTGGGCTTGGTAGTG SEQ ID No 214 AAGCTGGGGCCTGAAGGGGAG SEQ ID No 215 AAGGGGAGCTGCTTATCCGCT SEQ ID No 216 AACTCCTTCAATGAGGCCACC SEQ ID No 217 AATGAGGCCACCATGGTTCTG SEQ ID No 218 AAGATCGTGGAGATGGAGGAT SEQ ID No 219 AAGTACATTCTGTGCTGCCTG SEQ ID No 220 AAAAACCCCTACCGCTTCCTG SEQ ID No 221 AAAACCCCTACCGCTTCCTGT SEQ ID No 222 AAACCCCTACCGCTTCCTGTG SEQ ID No 223 AACCCCTACCGCTTCCTGTGG SEQ ID No 224 AAGTGCGTGGAGGAGAATAAT SEQ ID No 225 AATAATGGCGTGGCCAAGCAC SEQ ID No 226 AATGGCGTGGCCAAGCACATC SEQ ID No 227 AAGCACATCAGCCGTTTCATC SEQ ID No 228 AACATGGACGGTGCCGCGCTC SEQ ID No 229 AAAGATCATCACCATCCTGGT SEQ ID No 230 AAGATCATCACCATCCTGGTC SEQ ID No 231 AAGCAGTCAACCTCCCGGTCG SEQ ID No 232 AACCTCCCGGTCGACCATATC SEQ ID No 233 AATGTAGAAGGTGACGCTCTG SEQ ID No 234 AAGGTGACGCTCTGGGGGCAG SEQ ID No 235 AAAATTACGTGGACCGTACGG SEQ ID No 236 AAATTACGTGGACCGTACGGA SEQ ID No 237 AATTACGTGGACCGTACGGAG SEQ ID No 238 AAGCACAGAGCCTGAGTTGAT SEQ ID No 239 AAGTGAAGAGTGAGCTGCCCC SEQ ID No 240 AAGAGTGAGCTGCCCCTGGAT SEQ ID No 241 AAGGAAACCCCCTCCTCAAAC SEQ ID No 242 AAACCCCCTCCTCAAACACTA SEQ ID No 243 AAACACTATCGGGGGCCCGCA SEQ ID No 244 AACACTATCGGGGGCCCGCAG SEQ ID No 245 AAGAGAGGAATATCACCGGAA SEQ ID No 246 TATCACCGGAACCAGGGTGAA SEQ ID No 247 GCAGGAGGTGGAGGGGATGAA SEQ ID No 248 CTTTGGTGTGGCGCTGCGGAA SEQ ID No 249 CTGCGGAAGCTGGGGCCTGAA SEQ ID No 250 GCTGCTTATCCGCTTCTTCAA SEQ ID No 251 CCGCTTCTTCAACTCCTTCAA SEQ ID No 252 CATGTTCCTGGTGGCTGGCAA SEQ ID No 253 ACTCTTTGCCCGCCTTGGCAA SEQ ID No 254 CTACTTCCTCTTCACCCGCAA SEQ ID No 255 TACTTCCTCTTCACCCGCAAA SEQ ID No 256 CTTCCTCTTCACCCGCAAAAA SEQ ID No 257 CACGCTGCCGCTGATGATGAA SEQ ID No 258 GATGAAGTGCGTGGAGGAGAA SEQ ID No 259 GAAGTGCGTGGAGGAGAATAA SEQ ID No 260 GGAGAATAATGGCGTGGCCAA SEQ ID No 261 GCCCATCGGCGCCACCGTCAA SEQ ID No 262 GCAGTCCTTGGACTTCGTAAA SEQ ID No 263 AGCAGTCCTTGGACTTCGTAA SEQ ID No 264 CATCATCCTCGAAGCAGTCAA SEQ ID No 265 ACTCTGGCCATCATCCTCGAA SEQ ID No 266 TGTACCGTCCTCAATGTAGAA SEQ ID No 267 CCGGTCCTGTACCGTCCTCAA SEQ ID No 268 GGGGGCAGGACTCCTCCAAAA SEQ ID No 269 TGGGGGCAGGACTCCTCCAAA SEQ ID No 270 CTGGGGGCAGGACTCCTCCAA SEQ ID No 271 TGGACCGTACGGAGTCGAGAA SEQ ID No 272 ACAGAGCCTGAGTTGATACAA SEQ ID No 273 GCCTGAGTTGATACAAGTGAA SEQ ID No 274 CTGCCAGTCCCCACTGAGGAA SEQ ID No 275 CAGTCCCCACTGAGGAAGGAA SEQ ID No 276 GGAAGGAAACCCCCTCCTCAA SEQ ID No 277 GAAGGAAACCCCCTCCTCAAA SEQ ID No 278 TGCCACGGTCGCCTCTGAGAA SEQ ID No 279 ACGGTCGCCTCTGAGAAGGAA SEQ ID No 280 GAGAAGGAATCAGTCATGTAA SEQ ID No 281 GAGAGGAATATCACCGGAA SEQ ID No 282 GCTGGGGCCTGAAGGGGAG SEQ ID No 283 TAATGGCGTGGCCAAGCAC SEQ ID No 284 TGGCGTGGCCAAGCACATC SEQ ID No 285 CATGGACGGTGCCGCGCTC SEQ ID No 286 AATTACGTGGACCGTACGG SEQ ID No 287 ATTACGTGGACCGTACGGA SEQ ID No 288 TTACGTGGACCGTACGGAG SEQ ID No 289 GCACAGAGCCTGAGTTGAT SEQ ID No 290 GAGAGGAATATCACCGGAA SEQ ID No 291 AGAATAATGGCGTGGCCAA SEQ ID No 292 TCATCCTCGAAGCAGTCAA SEQ ID No 293 GGTCCTGTACCGTCCTCAA SEQ ID No 294 GACCGTACGGAGTCGAGAA SEQ ID No 295 AGAGCCTGAGTTGATACAA SEQ ID No 296 CCACGGTCGCCTCTGAGAA SEQ ID No 297 GGTCGCCTCTGAGAAGGAA

The ASCT2 gene specificity was confirmed by searching NCBI BlastN database. The siRNAs were chemically synthesized.

All of the forty-two purified siRNA duplexes were complexed with lipofectamine and added to the cells for 12 h in serum-free medium. Thereafter, cells were cultured for 72-96 h in serum-supplemented medium, which was replaced by serum-free medium 24 h before the experiments. A scrambled negative siRNA duplex was used as control.

The ASCT2-siRNA is directed to a single target ASCT2 gene sequence. Alternatively, the siRNA is directed to multiple target ASCT2 gene sequences. For example, the composition contains ASCT2-siRNA directed to two, three, four, five or more ASCT2 target sequences. By ASCT2 target sequence is meant a nucleotide sequence that is identical to a portion of the ASCT2 gene. The target sequence can include the 5′ untranslated (UT) region, the open reading frame (ORF) or the 3′ untranslated region of the human ASCT2 gene. Alternatively, the siRNA is a nucleic acid sequence complementary to an upstream or downstream modulator of ASCT2 gene expression. Examples of upstream and downstream modulators include, a transcription factor that binds the ASCT2 gene promoter, a kinase or phosphatase that interacts with the ASCT2 polypeptide, a ASCT2 promoter or enhance.

ASCT2-siRNA which hybridize to target mRNA decrease or inhibit production of the ASCT2 polypeptide product encoded by the ASCT2 gene by associating with the normally single-stranded mRNA transcript, thereby interfering with translation and thus, expression of the protein. Exemplary nucleic acid sequence for the production of ASCT2-siRNA include the sequences of nucleotides 300-320 (SEQ ID NO: 209), 452-472 (SEQ ID NO: 216), 773-793 (SEQ ID NO: 225), 776-796 (SEQ ID NO: 226), 830-850 (SEQ ID NO: 228), 1122-1142 (SEQ ID NO: 235), 1123-1143 (SEQ ID NO: 236), 1124-1144 (SEQ ID NO: 237), 1150-1170 (SEQ ID NO: 238), 769-789 (SEQ ID NO: 260), 994-1014 (SEQ ID NO: 264), 1066-1086 (SEQ ID NO: 267), 1131-1151 (SEQ ID NO: 271), 1154-1174 (SEQ ID NO: 272), 1264-1284 (SEQ ID NO: 278), 1268-1288 (SEQ ID NO: 279), 302-320 (SEQ ID NO: 281), 454-472 (SEQ ID NO: 282), 775-793 (SEQ ID NO: 283), 778-796 (SEQ ID NO: 284), 832-850 (SEQ ID NO: 285), 1124-1142 (SEQ ID NO: 286), 1125-1143 (SEQ ID NO: 287), 1126-1144 (SEQ ID NO: 288), 1152-1170 (SEQ ID NO: 289), 771-789 (SEQ ID NO: 291), 996-1014 (SEQ ID NO: 292), 1068-1086 (SEQ ID NO: 293), 1133-1151 (SEQ ID NO: 294), 1156-1174 (SEQ ID NO: 295), 1266-1284 (SEQ ID NO: 296), 1270-1288 (SEQ ID NO: 297) as the target sequence. Furthermore, in order to enhance the inhibition activity of the siRNA, nucleotide “u” can be added to 3′ end of the antisense strand of the target sequence.

Preferably at least 2, more preferably 2 to 10, and most preferably 2 to 5 u's are added. The added u's form single strand at the 3′ end of the antisense strand of the siRNA.

The ASCT2-siRNA can be directly introduced into the cells in a form that is capable of binding to the mRNA transcripts. Alternatively, a vector encoding the ASCT2-siRNA can be introduced into the cells.

A loop sequence consisting of an arbitrary nucleotide sequence can be located between the sense and antisense sequence in order to form a hairpin loop structure. Thus, the present invention also provides siRNA having the general formula 5′-[A]-[B]-[A′]-3′, wherein [A] is a ribonucleotide sequence corresponding to a target sequence of the ASCT2 gene. Preferably [A] is a sequence selected from the group consisting of nucleotides 300-320 (SEQ ID NO: 209), 452-472 (SEQ ID NO: 216), 773-793 (SEQ ID NO: 225), 776-796 (SEQ ID NO: 226), 830-850 (SEQ ID NO: 228), 1122-1142 (SEQ ID NO: 235), 1123-1143 (SEQ ID NO: 236), 1124-1144 (SEQ ID NO: 237), 1150-1170 (SEQ ID NO: 238), 769-789 (SEQ ID NO: 260), 994-1014 (SEQ ID NO: 264), 1066-1086 (SEQ ID NO: 267), 1131-1151 (SEQ ID NO: 271), 1154-1174 (SEQ ID NO: 272), 1264-1284 (SEQ ID NO: 278), 1268-1288 (SEQ ID NO: 279), 302-320 (SEQ ID NO: 281), 454-472 (SEQ ID NO: 282), 775-793 (SEQ ID NO: 283), 778-796 (SEQ ID NO: 284), 832-850 (SEQ ID NO: 285), 1124-1142 (SEQ ID NO: 286), 1125-1143 (SEQ ID NO: 287), 1126-1144 (SEQ ID NO: 288), 1152-1170 (SEQ ID NO: 289), 771-789 (SEQ ID NO: 291), 996-1014 (SEQ ID NO: 292), 1068-1086 (SEQ ID NO: 293), 1133-1151 (SEQ ID NO: 294), 1156-1174 (SEQ ID NO: 295), 1266-1284 (SEQ ID NO: 296), 1270-1288 (SEQ ID NO: 297); [B] is a ribonucleotide sequence consisting of 3 to 23 nucleotides; and [A′] is a ribonucleotide sequence consisting of the complementary sequence of [A]. The region [A] hybridizes to [A′], and then a loop consisting of region [B] is formed. The loop sequence may be preferably 3 to 23 nucleotide in length. Suitable loop sequences are described at www.ambion.com/techlib/tb/tb_506.html. Furthermore, loop sequence consisting of 23 nucleotides also provides active siRNA (Jacque et al., 2002). Preferred loop sequences included:

-   -   AUG: (Sui et al., 2002).     -   CCC, CCACC or CCACACC: (Paul et al., 2002).     -   UUCG: (Lee et al., 2002).     -   CTCGAG or AAGCUU: (Biology, 2003).     -   UUCAAGAGA: (Yu et al., 2002).

The loop sequence can be selected from group consisting of AUG, CCC, UUCG, CCACC, CTCGAG, AAGCUU, CCACACC, and UUCAAGAGA. Preferably the loop sequence is UUCAAGAGA (“ttcaagaga” in DNA).

The inventors have surprisingly found that siRNAs targeted to certain target sequences of the LAT1 gene or ASCT2 gene are particularly effective at inhibiting sodium-independent [¹⁴C]-L-leucine uptake or sodium-dependent [¹⁴C]-L-alanine uptake, respectively, LAT1 or ASCT2 expression, cell growth and growth of tumors overexpressing LAT1 and/or ASCT2 transporters.

In a specific embodiment of the present invention, the sense strand of the LAT1 siRNA used in the present invention comprises or consists of a sequence selected from the group comprising SEQ ID NOS 6, 22, 34, 58 and 61. The siRNA also comprises a corresponding antisense strand. The use of such an siRNA has been found to be particularly effective in inhibiting sodium-independent [¹⁴C]-L-leucine transport. In a further embodiment, the sense strand of the LAT1 siRNA comprises or consists of at least one sequence selected from the group comprising SEQ ID NO: 110, 126, 138, 162 and 165.

According to a another aspect of the present invention there is provided a siRNA comprising a sense LAT1 nucleic acid and an anti-sense LAT1 nucleic acid, and the sense LAT1 nucleic acid is substantially identical to a target sequence contained within LAT1 mRNA and the anti-sense LAT1 nucleic acid is complementary to the sense LAT1 nucleic acid. The sense and antisense nucleic acids hybridize to each other to form a double-stranded molecule.

The siRNA molecules of the present invention have the property to inhibit expression of the LAT1 gene when introduced into a cell expressing said gene.

The siRNA molecules of the present invention have the property to inhibit cell growth when introduced into a cell expressing LAT1 gene.

The siRNA molecules of the present invention have the property to inhibit tumour growth when introduced into a tumour expressing LAT1 gene.

In a specific embodiment of the present invention, the sense strand of the ASCT2 siRNA used in the present invention comprises or consists of a sequence selected from the group comprising SEQ ID NOS 225, 237, 267 and 278. The siRNA also comprises a corresponding antisense strand. The use of such an siRNA has been found to be particularly effective in inhibiting sodium-independent [¹⁴C]-L-leucine transport. In a further embodiment, the sense strand of the LAT1 siRNA comprises or consists of at least one sequence selected from the group comprising 314, 326, 356 and 367.

According to a another aspect of the present invention there is provided a siRNA comprising a sense ASCT2 nucleic acid and an anti-sense ASCT2 nucleic acid, and the sense ASCT2 nucleic acid is substantially identical to a target sequence contained within ASCT2 mRNA and the anti-sense ASCT2 nucleic acid is complementary to the sense ASCT2 nucleic acid. The sense and antisense nucleic acids hybridize to each other to form a double-stranded molecule.

The siRNA molecules of the present invention have the property to inhibit expression of the ASCT2 gene when introduced into a cell expressing said gene.

The siRNA molecules of the present invention have the property to inhibit cell growth when introduced into a cell expressing ASCT2 gene.

The siRNA molecules of the present invention have the property to inhibit tumour growth when introduced into a tumour expressing ASCT2 gene.

When combined the siRNA-LAT1 and siRNA-ASCT2 of the present invention have the property to inhibit expression of the LAT1 and ASCT2 genes when introduced into a cell expressing said gene.

When combined the siRNA-LAT1 and siRNA-ASCT2 molecules of the present invention have the property to inhibit cell growth when introduced into a cell expressing the LAT1 and ASCT2 genes.

When combined the siRNA-LAT1 and siRNA-ASCT2 molecules of the present invention have the property to inhibit tumour growth when introduced into a tumour expressing and LAT1 ASCT2 genes.

Another aspect of the invention relates to nucleic acid sequences and vectors encoding the siRNA according to the fourth aspect of the present invention, as well as to compositions comprising them, useful, for example, in the methods of the present invention. Compositions of the present invention may additionally comprise transfection enhancing agents. The nucleic acid sequence may be operably linked to an inducible or regulatable promoter. Suitable vectors are discussed above. Preferably the vector is an adeno-associated viral vector.

The composition of the present invention may additionally comprise a pharmaceutical agent for treating cancer, wherein the agent is different from the siRNA. Preferably the pharmaceutical agent is selected from the group consisting of abarelix, amifostine, aminoglutethimide, anastrozole, bevacizumab, bicalutamide, bleomycin, bortezomib, busulfan, capecitabine, carboplatin, carmustine, cetuximab, chlorambucil, cispatlin, cladribine, cyclophosphamide, cytarabine, dacarbazine, dactinomycin, daunorubicin, docetaxel, doxorubicin, erlotinib, 4′-epidoxorubicin, epirubicin, estramustine, etoposide, floxuridine, fludarabine, 5-fluorouracil, flutamide, gefitinib, gemcitabine, goserelin, hexamethylmelamine, hydroxyurea, ifosfamide, imatinib, irinotecan, leuprolide, megestrol, melphalan, 6-mercatopurine, methotrexate, mitomycin, mitotane, mitoxantrone, oxaliplatin, paclitaxel, pentostatin, prednisone, procarbazine, rituximab, satraplatin, tamoxifen, temozolomide, teniposide, 6-thioguanine, thiotepa, topotecan, toremifen, trastuzumab, triptorelin, valrubicin, vinblastine, vincristine and vinolrebine.

Non-viral delivery siRNA systems involve the creation of nucleic acid transfection reagents. Nucleic acid transfection reagents have two basic properties. First, they must interact in some manner with the nucleic acid cargo. Most often this involves electrostatic forces, which allow the formation of nucleic acid complexes. Formation of a complex ensures that the nucleic acid and transfection reagents are presented simultaneously to the cell membrane. Complexes can be divided into three classes, based on the nature of the delivery reagent: lipoplexes; polyplexes; and lipopolyplexes. Lipoplexes are formed by the interaction of anionic nucleic acids with cationic lipids, polyplexes by interaction with cationic polymers. Lipopolyplex reagents can combine the action of cationic lipids and polymers to deliver nucleic acids. Addition of histone, poly-L-lysine and protamine to some formulations of cationic lipids results in levels of delivery that are higher than either lipid or polymer alone. The combined formulations might also be less toxic. The biocompatible systems most relevant to this purpose are non-viral biodegradable nanocapsules designed especially according to the physical chemistry of nucleic acids. They have an aqueous core surrounded by a biodegradable polymeric envelope, which provides protection and transport of the siRNA into the cytosol and allow the siRNA to function efficiently in vivo.

The present invention also provides a cell containing the siRNA according to the fourth aspect of the present invention or the vector of the present invention. Preferably the cell is a mammalian cell, more preferably a human cell. It is further preferred that the cell is an isolated cell.

While the foregoing disclosure provides a general description of the subject matter encompassed within the scope of the present invention, including methods, as well as the best mode thereof, of making and using this invention, the following examples are provided to further enable those skilled in the art to practice this invention and to provide a complete written description thereof. However, those skilled in the art will appreciate that the specifics of these examples should not be read as limiting on the invention, the scope of which should be apprehended from the claims and equivalents thereof appended to this disclosure. Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

All documents mentioned in this specification, including reference to sequence database identifiers, are incorporated herein by reference in their entirety. Unless otherwise specified, when reference to sequence database identifiers is made, the version number is 1.

“and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example “A and/or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described. The invention is further described in the following non-limiting examples.

The following examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.

DESCRIPTION OF THE DRAWINGS

FIG. 1. Relative abundance of LAT1 protein and ASCT2 protein in human liver carcinoma SK-HEP-1 cells, human bladder carcinoma T24 cells, human fibrosarcoma HT-1080 cells and human colon cancer HTC-116 cells by western blot (relative to GAPDH).

FIG. 2. Relative abundance of LAT1 mRNA and ASCT2 mRNA in in human liver carcinoma SK-HEP-1 cells, human bladder carcinoma T24 cells, human fibrosarcoma HT-1080 cells and human colon cancer HTC-116 cells by RT-PCR (relative to GAPDH).

FIG. 3. Transport of ¹⁴C-L-leucine through LAT1 (sensitive to unlabelled L-leucine) and the transport of ¹⁴C-L-alanine through ASCT2 (sensitive to unlabelled L-alanine). Significantly different from corresponding control values (****p<0.001).

FIG. 4. LAT1 mRNA relative abundance in liver carcinoma SK-HEP-1 cells treated for 24 h with 10 nM siRNA-LAT1 (A) against nucleotide SEQ ID NO: 6, 22, 34, 58 and 61 and (B) ASCT2 mRNA relative abundance in liver carcinoma SK-HEP-1 cells treated for 6 h with 10 nM siRNA-ASCT2 against nucleotide SEQ ID NO: 225, 237, 267 and 278 on ASCT2 mRNA levels in human cancer cells (SK-HEP-1) using 0.5% Lipofectamine 2000 as the transfecting agent at 24 h. Significantly different from corresponding control values (*p<0.01) and values for SEQ ID NO: 34 (# p<0.05).

FIG. 5. [¹⁴C]-L-leucine (0.25 μM) (A and C) and [¹⁴C]-L-alanine (0.25 μM) (B and D) uptake at initial rate of uptake (1 min) in liver carcinoma SK-HEP-1 cells treated for 6 h with 10 nM siRNA-LAT1 (A and C) against nucleotide SEQ ID NO: 6, 22, 34, 58 and 61 anti-LAT1 against nucleotide SEQ ID NOS 6, 22, 34, 58 and 61 (A and C) and SEQ ID NO: 6, 22, 34, 58 and 61 on and 10 nM siRNA-ASCT2 against nucleotide SEQ ID NO: 225, 237, 267 and 278 using 0.4% Lipofectamine 2000 as the transfecting agent at 24 h (A and B) or 48 h (C and D). Significantly different from corresponding control values (*p<0.01), values for SEQ ID NO: 34 (# p<0.05) and values for SEQ ID NO: 267 ($ p<0.05).

FIG. 6. 5′ DNA sense, 5′ sense siRNA and 3′ antisense siRNA-LAT1 against nucleotide SEQ ID NO: 58/162/411, 58/387/388, 58/389/390, 58/389/412, 61/165/396, 61/391/392, 61/393/394 and 61/395/396.

FIG. 7. 5′ DNA sense, 5′ sense siRNA and 3′ antisense siRNA-ASCT2 against nucleotide SEQ ID NO: 267/356/402, 267/397/398, 267/399/400, 267/401/402, 278/367/408, 278/403/404, 278/405/406 and 278/407/408.

FIG. 8. [¹⁴C]-L-leucine (0.25 μM) (A) and [¹⁴C]-L-alanine (0.25 μM) (B) uptake at initial rate of uptake (1 min) in human fibrosarcoma HT-1080 cells treated for 6 h with 5 nM anti-LAT1 against nucleotide SEQ ID NO: 58/162/411, 58/387/388, 61/165/396, 61/391/392 and and one commercially available siRNA (SI31011000 from QIAGEN) 5 nM siRNA-ASCT2 against nucleotide SEQ ID NO: 267/356/402, 267/397/398, 278/367/408, 278/403/404 and one commercially available siRNA (SI00097930, from QIAGEN) using 0.4% Lipofectamine 2000 as the transfecting agent at 48 h. Significantly different from corresponding control values (*p<0.01) and values for SEQ ID NO: 267/397/398 ($ p<0.05).

FIG. 9. LAT1 mRNA (A and C) and ASCT2 mRNA (B and D) relative abundance in human colon cancer HTC-116 cells treated for 6 h with 5 or 25 nM siRNA-LAT1 against nucleotide SEQ ID NO: 58/162/411, 61/165/396, 58/387/388 and 61/391/392 and ASCT2 mRNA relative abundance in human colon cancer HTC-116 cells treated for 6 h with 5 or 25 nM siRNA-ASCT2 against nucleotide SEQ ID NO: 267/356/402, 278/367/408, 267/397/398 and 278/403/404 using 0.5% Lipofectamine 2000 as the transfecting agent at 24 h (A and B) or 72 h (C and D). Significantly different from corresponding control values (*p<0.01).

FIG. 10. LAT1 mRNA relative abundance in human colon cancer HTC-116 cells treated for 6 h with (A) 5, 25 and 45 nM siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388, using (B) 0.5% Lipofectamine 2000®, Lipofectamine RNAiMAX® or Injectin® as the transfecting agents at 72 h. Significantly different from corresponding control values (**p<0.01, ***p<0.02; ****p<0.001) and corresponding values with Injectin® (# p<0.05).

FIG. 11. Effect of transfecting agents Lipofectamine 2000® or Injectin® upon human colon cancer HTC-116 cell density after 72 h exposure. Significantly different from corresponding control values (**p<0.01, ***p<0.02).

FIG. 12. siRNA complexation analysis by agarose gel electrophoresis in the siRNA:Injectin® complexes at (A) 20 μL and (B) 80 μL complex volumes. In panel A, electrophoresis of siRNA:Injectin® complexes revealed that siRNA is fully complexed when the siRNA:Injectin® ratio is 1:1 and the percentage of Injectin® in the complex mixture is higher than 0.9%. In panel B, siRNA complexation is not effective when the siRNA:Injectin® ratio 1:1 is maintained but the amount of Injectin® in the complex mixture is equal or lower than 0.2%.

FIG. 13. Effects of negative control siRNA commercial (from QIAGEN) sequences NC-SI03650318 and NC-SI03650325 upon proliferation human colon cancer HTC-116 cells at 72 h exposure times using Injectin® (0.075 and 0.1%) or Lipofectamine 2000® (0.25%) as the transfecting agent.

FIG. 14. Effects of (A) siRNA-LAT1 against nucleotide SEQ ID NO: 6, 22, 34, 58/162/411, 58/387/388, 58/389/390, 58/389/412, 61/165/396, 61/391/392, 61/393/394, 61/395/396 and three commercially available siRNAs (SI31011000, HSS112005 and SASI_Hs01_00103513 respectively from QIAGEN, Thermofisher Scientific and Sigma-Aldrich) and (B) siRNA-ASCT2 against nucleotide SEQ ID NO: 225, 237, 267/356/402, 267/397/398, 267/399/400, 267/401/402, 278/367/408, 278/403/404, 278/405/406, 278/407/408 and one commercially available siRNA (SI00097930, from QIAGEN), respectively, upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using 0.1% Injectin® as the transfecting agent. In panel A, values were significantly different from corresponding control values (*p<0.01), values for SEQ ID NO: 34 (# p<0.05) and values for SEQ ID NO: 58 ($ p<0.05). In panel B, values were significantly different from corresponding control values (*p<0.01), values for SEQ ID NO: 267 (# p<0.05) and values for SEQ ID NO: 278 ($ p<0.05).

FIG. 15. Effects of siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 and siRNA-ASCT2 against nucleotide SEQ ID NO: 267/397/398 and 278/403/404 upon proliferation human colon cancer HTC-116 cells at 72 h exposure times using increasing concentrations (0.037% to 0.15%) of Injectin® as the transfecting agent. Significantly different from corresponding control values (*p<0.05, **p<0.01, ***p<0.02; ****p<0.001) and corresponding values with Injectin® (# p<0.05).

FIG. 16. Effects of 5-fluoruracil (5-FU; 3 and 10 μM), cisplatin (Cisp; 3 and 10 μM) and oxaliplatin (Oxa; 1 and 3 μM) alone or in combination with siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 (5 and 25 nM) upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using increasing concentrations using 0.25% Lipofectamine 2000 as the transfecting agent. Significantly different from corresponding control values (# p<0.05, ####p<0.001) and corresponding values with the antineoplastic cytotoxic agent 5-FU, Cisp or Oxa (*p<0.05 **p<0.01, ***p<0.02, ****p<0.001).

FIG. 17. Effects of 5-fluoruracil (5-FU; 10 μM) alone or in combination with anti-LAT1 SEQ ID NOS 58/387/388 and 61/391/392 (25 nM) upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using 0.037% Injectin® as the transfecting agent. Significantly different from corresponding control values (#### p<0.001) and corresponding values with the antineoplastic cytotoxic agent 5-FU (**p<0.01, ***p<0.001).

FIG. 18. Effects of anti-LAT1 SEQ ID NOS 58/387/388 and 61/391/392 (25 nM) and anti-ASCT2 SEQ ID NOS 267/397/398 and 278/403/404 alone or in combination upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using Injectin® as the transfecting agent. Significantly different from corresponding control values (*p<0.05**p<0.01, ***p<0.02, ****p<0.001).

FIG. 19. Effects of anti-LAT1 SEQ ID NOS 58/162/411, 58/387/388, 58/389/390, 61/165/396, 61/391/392, 61/393/394 and two commercially available siRNAs (SI31011000 and HSS112005, respectively from QIAGEN and Thermofisher Scientific) upon (A) LAT1 mRNA relative abundance and (B) upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using 0.17% Lipofectamine 2000® or 0.1% Injectin® as the transfecting agent. Significantly different from corresponding control values (*p<0.01), values for SEQ ID NO: 58 (#p<0.05) and values for SEQ ID NO: 61 ($ p<0.05).

FIG. 20. Effects of anti-ASCT2 SEQ ID NOS 267/356/402, 267/397/398, 267/399/400, 278/367/408, 278/403/404, 278/405/406 and one commercially available siRNA (SI00097930, from QIAGEN) upon (A) ASCT2 mRNA relative abundance and (B) upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times using 0.17% Lipofectamine 2000® or 0.1% Injectin® as the transfecting agent. Significantly different from corresponding control values (*p<0.01), values for SEQ ID NO: 267 (# p<0.05) and values for SEQ ID NO: 278 ($ p<0.05).

FIG. 21. Representative western blot of LAT1 and ASCT2 proteins in the xenograft tumour model developed in immune deficient mice injected subcutaneously with human colon cancer HTC-116 cells.

FIG. 22. Relative abundance of LAT1 mRNA and ASCT2 mRNA by RT-PCR (relative to GAPDH) and relative abundance of LAT1 protein and ASCT2 protein by western blot (relative to GAPDH) in the xenograft tumour model developed in immune deficient mice injected subcutaneously with human colon cancer HTC-116 cells.

FIG. 23. Relative tumour volume in the xenograft tumour model developed in immune deficient mice injected subcutaneously with human colon cancer HTC-116 cells and treated every other day with intratumoral injections (50 μL) of vehicle (Injectin®) or anti-LAT1 SEQ ID NO: 58/387/388 (10 μg) and anti-ASCT2 SEQ ID NO: 278/403/404 (10 μg). The reduction in relative tumor volume induced by SEQ ID NO: 58/387/388 and SEQ ID NO: 278/403/404 was statistically significant with p values of 0.0018 and 0.0051, respectively.

FIG. 24. Table of LAT1 preferred target sequences.

FIG. 25. Table of ASCT2 preferred target sequences.

FIGS. 26A-D. Table of LAT 1 target sequences and siRNA. Figure discloses 5′ anti-sense sequences as SEQ ID NOS 413-516, respectively, in order of appearance.

FIGS. 27A-C. Table of ASCT2 target sequences and siRNA. Figure discloses 5′ anti-sense sequences as SEQ ID NOS 517-605, respectively, in order of appearance.

MATERIALS AND METHODS

Cell Culture

SK-HEP-1, T24, HT-1080 and HCT-116 cell lines were maintained in a humidified atmosphere of 5% CO₂ at 37° C. SK-HEP-1 cells were grown in RPMI-1640 (Sigma, St. Louis, Mo.) supplemented with 20% fetal bovine serum (FBS) (Gibco, UK), 100 U/mL penicillin G, 0.25 μg/mL amphotericin B, 100 μg/mL streptomycin (Gibco, UK), 25 mM sodium bicarbonate (Merck, Germany) and 25 mM N-2-hydroxyethylpiperazine-N′-2-ethanosulfonic acid (HEPES) (Sigma, St. Louis, Mo.). T24 and HT-1080 cells were grown, respectively, in Dulbecco's Modified Eagle's Medium (DMEM)—high glucose (Sigma, St. Louis, Mo.) and DMEM—low glucose (Sigma, St. Louis, Mo.), supplemented with 10% FBS (Gibco, UK), 100 U/mL penicillin G, 0.25 μg/mL amphotericin B, 100 μg/mL streptomycin (Gibco, UK), 25 mM sodium bicarbonate (Merck, Germany) and 25 mM HEPES (Sigma, St. Louis, Mo.). HCT-116 cells were grown in McCoy's 5A (Sigma, St. Louis, Mo.) supplemented with 10% FBS (Gibco, UK), 100 U/mL penicillin G, 0.25 μg/mL amphotericin B, 100 μg/mL streptomycin (Gibco, UK), 25 mM sodium bicarbonate (Merck, Germany) and 25 mM HEPES (Sigma, St. Louis, Mo.). For all cell lines the medium was changed every 2 days, and cells reached confluence 3-4 days after initial seeding. For subculturing, cells were dissociated with 0.25% trypsin-ethylenediaminetetraacetic acid (EDTA) (Sigma, St. Louis, Mo.), split 1:15 or 1:20 and subcultured in a 21-cm² growth area (Sarstedt, Germany).

LAT1 and ASCT2 Protein Expression

Cells were rinsed twice with cold phosphate-buffered saline (PBS) and incubated with 100 μL RIPA lysis buffer (154 mM NaCl, 65.2 mM TRIZMA base, 1 mM EDTA, 1% NP-40 (IGEPAL), 6 mM sodium deoxycholate) containing protease inhibitors: 1 mM PMSF, 1 μg/mL leupeptine and 1 μg/mL aprotinin; and phosphatase inhibitors: 1 mM Na₃VO₄ and 1 mM NaF. Cells were scraped and briefly sonicated. Equal amounts of total protein (30 μg) were separated on a 10% SDS-polyacrylamide gel and electrotransferred to a nitrocellulose membrane in Tris-Glycine transfer buffer containing 20% methanol. The transblot sheets were blocked in 5% non-fat dry milk in Tris-buffered saline (TBS) for 60 min and then incubated overnight, at 4° C., with the following antibodies: rabbit anti-LAT1 (1:1000; Cell Signalling); rabbit anti-ASCT2 (1:1000; Cell Signalling); or mouse monoclonal anti-GAPDH (1:20,000; Santa Cruz Biotechnology Inc.), diluted in 2.5% non-fat dry milk in TBS-Tween 20 (0.1% vol/vol). The immunoblots were subsequently washed and incubated with fluorescently-labelled goat anti-rabbit (1:20,000; IRDye™ 800, Rockland) or fluorescently-labelled goat anti-mouse secondary antibody (1:20,000; AlexaFluor 680, Molecular Probes) for 60 min at room temperature (RT) and protected from light. Membranes were washed and imaged by scanning at both 700 nm and 800 nm with an Odyssey Infrared Imaging System (LI-COR Biosciences).

LAT1 and ASCT2 Gene Expression

Total RNA was isolated and purified using the SV Total RNA Isolation System (Promega, USA) according to manufacturer's instructions. RNA quality and concentration were verified in the NanoDrop ND1000 Spectrophotometer (Thermo Scientific, USA), and RNA integrity and genomic DNA contamination were evaluated by agarose gel electrophoresis. Total RNA (1 μg) was converted into cDNA using the Maxima Scientific First Strand cDNA Synthesis Kit for RT-qPCR (Thermo Scientific, USA), according to instructions. The following protocol was used: 1^(st) step, 10 min at 25° C.; 2^(nd) step, 15 min at 50° C.; 3^(rd) step, 5 min at 85° C. cDNA was used for qPCR analysis using Maxima SYBR Green qPCR Master Mix (Thermo Scientific, USA) in the StepOnePlus instrument (Applied Biosystems, USA). QuantiTect Primer Assay for LAT1 and ASCT2 and for the endogenous control gene GAPDH (Quiagen, Germany) were used. The qPCR reaction was performed in 96-well PCR plates (Sarstedt, Germany) as follows: one cycle of 10 min at 95° C., followed by 40 PCR cycles at 95° C. 15 s and 60° C. 60 s. A melting curve was made immediately after the qPCR, to demonstrate the specificity of the amplification. No template controls were always evaluated for each target gene. Quantification cycle (Cq) values were generated automatically by the StepOnePlus 2.3 Software and the ratio of the target gene was expressed in comparison to the endogenous control gene GAPDH. Real-time PCR efficiencies were found to be between 90% and 110%.

LAT1 Activity

Cells were plated in 24-well plates (Sarstedt, Germany) and grown until confluence was reached. On the day of the experiment, cell culture medium was aspirated and cells were preincubated for 15 min in Hanks' medium (NaCl 140 mM, KCl 5 mM, MgSO₄.7H₂O 0.8 mM, K₂HPO₄ 0.33 mM, KH₂PO₄ 0.44 mM, MgCl₂.6H₂O 1 mM, CaCl₂) 0.025 mM, Tris-HCl 9.75 mM, pH 7.4). Uptake was initiated by addition of Hanks' medium with 0.25 μM [¹⁴C]-L-leucine in the absence and in the presence of 3 mM unlabeled L-leucine. During preincubation and incubation cells were continuously shaken and maintained at 37° C. Uptake was terminated after 1 min by rapid removal of uptake solution by means of a vacuum pump connected to a Pasteur pipette, followed by a rapid wash with Hanks' medium. Subsequently, cells were solubilized in 0.1% vol/vol Triton X-100 (dissolved in 5 mM Tris-HCl, pH 7.4), and radioactivity was measured by liquid scintillation counting.

ASCT2 Activity

Cells were plated in 24-well plates (Sarstedt, Germany) and grown until confluence was reached. On the day of the experiment, Cell culture medium was aspirated and cells were preincubated for 15 min in Hanks' medium (ChCl 140 mM, KCl 5 mM, MgSO₄.7H₂O 0.8 mM, K₂HPO₄ 0.33 mM, KH₂PO₄ 0.44 mM, MgCl₂.6H₂O 1 mM, CaCl₂) 0.025 mM, Tris-HCl 9.75 mM, pH 7.4). Uptake was initiated by the addition of Hanks' medium with 0.25 μM [¹⁴C]-L-alanine in the absence and in the presence of 3 mM unlabeled L-alanin. During preincubation and incubation cells were continuously shaken and maintained at 37° C. Uptake was terminated after 1 min by rapid removal of uptake solution by means of a vacuum pump connected to a Pasteur pipette, followed by a rapid wash with Hanks' medium. Subsequently, cells were solubilized in 0.1% vol/vol Triton X-100 (dissolved in 5 mM Tris-HCl, pH 7.4), and radioactivity was measured by liquid scintillation counting.

LAT1 Gene Silencing

Cells were plated in 24-well (Sarstedt, Germany) or 6-well plates (Sarstedt, Germany) or 96-well plates with black walls clear bottom (BD Biosciences, USA) and incubated 24 h under normal growth conditions. siRNAs against LAT1 and transfection agent were diluted at desired concentrations and mixed according to transfection agent manufacturer's instructions. The mixture was incubated 20 min at RT for siRNA-complex formation, after which it was added to the cells and incubated at 37° C., 5% CO₂. After the incubation period, serum and antibiotic was restored and cells were further incubated at normal conditions for the desired time points until evaluation of LAT1 activity or LAT1 expression (immunoblotting and RT-qPCR).

ASCT2 Gene Silencing

Cells were plated in 24-well (Sarstedt, Germany) or 6-well plates (Sarstedt, Germany) or 96-well plates with black walls clear bottom (BD Biosciences, USA) and incubated 24 h under normal growth conditions. siRNAs against ASCT2 and transfection agent were diluted at desired concentrations and mixed according to transfection agent manufacturer's instructions. The mixture was incubated 20 min at RT for siRNA-complex formation, after which it was added to the cells and incubated at 37° C., 5% CO₂. After the incubation period, serum and antibiotic was restored and cells were further incubated at normal conditions for the desired time points until evaluation of ASCT2 activity or ASCT2 expression (immunoblotting and RT-qPCR).

Cell Proliferation Assay

Cell proliferation was measured using calcein-AM (Thermo Fisher Scientific, USA). The membrane permeant calcein-AM, a nonfluorescent dye, is taken up and converted by intracellular esterases to membrane impermeant calcein, which emits green fluorescence. Cells were plated in 96-well plates with black walls clear bottom (BD Biosciences, USA) and incubated 24 h under normal growth conditions. Cells were incubated with test items at 37° C., 5% C02. After the incubation period, serum and antibiotic was restored and cells were further incubated at normal conditions during 72 h. After treatment with test substances or vehicle, cells were washed twice with Hanks' medium and loaded with 2 μM calcein-AM in Hanks' medium, at at 37° C. for 30 min. Fluorescence was measured at 485 nm excitation and 530 nm emission wavelengths in a microplate spectrofluorometer (Gemini EM, Molecular Devices). Nine consecutive fluorescence measurements are performed per well, to allow fluorescence readings in the whole area of the well, which was then considered for the calculation of mean fluorescence per well. To determine minimum staining for calcein (calceinmin), eight wells were treated with ethanol 30 min before calcein-AM addition. The percent cell number is calculated as [(calcein_(sample))/(calcein_(control))]×100.

Animals and Tumour Implantation

Human colon cancer HTC-116 cells grown in tissue culture and 10⁷ cells per mouse were injected into the hind flank of female NMRI nu/nu mice. Once tumours have developed and tumour volumes reached randomisation criteria, therapy will commence by every other day daily, intra-tumoral injections. A vehicle treated group was included in the study as control. Female immunodeficient NMRI nu/nu mice from Charles River were used. The animals were delivered at the age of 4-6 weeks and are used for implantation after at least 1 week of quarantine. All animals interventions were performed in accordance with the European Directive number 86/609, and the rules of the “Guide for the Care and Use of Laboratory Animals”, 7th edition, 1996, Institute for Laboratory Animal Research (ILAR), Washington, D.C. Only animals with unobjectionable health were selected to enter testing procedures. During the experiments, animals were monitored at least daily. Each cage was labelled with a record card indicating animal source, gender, and the delivery date. Animals were numbered during tumour implantation or at the initiation of a dose finding experiment.

The tumour volume was determined by a two-dimensional measurement with callipers on the day of randomization (Day 0) and then twice weekly. Tumour volumes were calculated according to the following equation: Tumour Vol [mm³]=a [mm]×b ² [mm²]×0.5

where “a” is the largest diameter and “b” is the perpendicular diameter of the tumour representing an idealized ellipsoid.

The relative volume of an individual tumour on day X (RTV_(x)) was calculated by dividing the absolute volume [mm³] of the respective tumour on day X (T_(x)) by the absolute volume of the same tumour on the day of randomization, i. e. on day 0 (T₀), multiplied by 100, as shown by the following equation:

${{RTV}_{x}\lbrack\%\rbrack} = {\frac{T_{x}}{T_{0}} \times 100}$

RTVs were used for growth characterization and compound activity rating as follows:

Rating RTV_(x) [%] CR Complete remission  ≤10 PR Partial remission >10; ≤50 MR Minor remission >50; ≤75 NC No change  >75; ≤125 P Progression >125

Group median and range (alternatively geometric mean+/−SEM) of RTVs were calculated, considering only the tumours of animals that were alive on the day in question (for median). Group median (geometric mean) RTVs were used for drawing tumour growth curves and for treatment evaluation.

Tumour inhibition on a particular day (T/C_(x)) was calculated from the median RTV of a test group and the median RTV of a control group multiplied by 100, as shown by the following equation:

$\frac{{T/{C_{x}\lbrack\%\rbrack}} = {{median}\mspace{14mu}{RTV}_{x}\mspace{14mu}{treated}\mspace{14mu}{group}}}{{median}\mspace{14mu}{RTV}_{x}\mspace{14mu}{control}\mspace{14mu}{group}} \times 100$

The optimum/minimum/best T/C [%] value recorded for a particular group during an experiment represents the maximum anti-tumour activity for the respective treatment and is rated as follows:

Rating T/C [%] − Inactive ≥65   +/− Borderline activity ≥50; ≤65 + Moderate activity ≥25; ≤50 ++ High activity ≥10; ≤25 +++ Very high activity  ≥5; ≤10 ++++ Complete remission <5

Tumour volume doubling/quadrupling time (DT/QT) is defined as the time interval (in days) required for a group to reach a median RTV of 200%/400% of the initial tumour volume. Growth delay is defined as the difference in days between the tumour volume doubling and quadrupling times of a test group and the respective control group.

Non-Viral Delivery siRNA Systems

1. Liposomes carrying therapeutic siRNA-LAT1 agents are capable of passing through the membrane of the target cell to deliver cargo. A large number of lipids can be used for the synthesis of liposomes used for the delivery of siRNAs. Neutral lipids that can be complexed with siRNA-LAT1 include DOPE (1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine), egg PC (phosphatidylcholine), DOPC (1,2-dioleoyl-sn-glycero-3-phosphatidylcholine and DPPE (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine).

2. Cationic lipids that can be complexed with siRNA-LAT1 include DOTAP (1,2-dioley-3-trimetylammonium propane), CDAN (N(1)-cholesteryloxycarbonyl-3,7-diazanonane-1,9-diamine)/DOPE, DC-Chol (3β-[N—(N′,N′-dimethylaminoethane)carbamoyl] cholesterol)/DOPE, DOTAP/DOPE, cationic lipid RPR209120 (2-(3-[Bis-(3-amino-propyl)-amino]-propylamino)-N-ditetradecylcarbamoylme-thyl-acetamide). Galactosylated (Gal-C4-Chol/DOPE) liposomes/siRNA-LAT1 complex can also induce gene silencing.

3. Cationic polymers can also be used in siRNA-LAT1 or siRNA-ASCT2 delivery. These materials combine with anionic siRNA-LAT1 or siRNA-ASCT2 to form a siRNA-LAT1-polymer complex or siRNA-ASCT2-polymer complex that can interact with the negatively charged cell surfaces through the cationic portion of the complex. Among the available polymers, polyethyleneimine (PEI) has the ability to bind strongly to negatively charged siRNA-LAT1 or siRNA-ASCT2. Biodegradable polymers such as poly(L-lysine) (PLL) are known for their lower toxicity and higher biocompatibility than PEI. A derivative of PLL, poly[a-(4-aminobutyl)-L-glycolic acid] exhibits higher transfection efficiency and lower immunogenicity and cytotoxicity than the original PLL polymer and can be used with siRNA-LAT1 or siRNA-ASCT2.

4. Cationized gelatin microspheres can be prepared by chemically cross-linking gelatin in the water-in-oil emulsion state. To impregnate siRNA-LAT1 or siRNA-ASCT2 expression plasmid DNA into cationized gelatin microspheres, PBS containing siRNA-LAT1 expression plasmid DNA can be dropped onto freeze-dried cationized gelatin microspheres and then kept for 24 h at 4° C.

5. Nanoparticles can be produced based on modified ionic gelation of tripolyphosphate (TPP) with chitosan. Two different types of chitosan (chitosan hydrochloride and glutamate) and each type with two different molecular weights can be used. Nanoparticles can be spontaneously obtained upon the addition of a TPP aqueous solution to chitosan solution under constant magnetic stirring at room temperature. The particles can then be incubated at room temperature for before use or further analysis. Nanoparticles are collected by centrifugation. The supernatants are discarded and nanoparticles are resuspended in filtered distilled water. For the association of siRNA-LAT1 or siRNA-ASCT2 with the chitosan-TPP nanoparticles (chitosan-TPP-siRNA-LAT1 or chitosan-TPP-siRNA-ASCT2), siRNA-LAT1 or siRNA-ASCT2 in double distilled water is added to the TPP solution before adding this drop-wise to the chitosan solution under constant magnetic stirring at room temperature. The particles are then incubated at room temperature before use or further analysis.

6. Chitosan (114 kDa) was dissolved in sodium acetate buffer to obtain a 0.2-1 mg/ml working solution range. Twenty microliters of siRNA-LAT1 or siRNA-ASCT2 (20-250 μm range) was added to 1 ml of filtered chitosan while stirring and left for 1 h. To calculate specific N:P ratios (defined as the molar ratio of chitosan amino groups/RNA phosphate groups) a mass per phosphate of 325 Da was used for RNA and mass per charge of 167.88 for chitosan (84% deacetylation).

7. The siRNA-LAT1 or siRNA-ASCT2 can be encapsulated in stable nucleic acid lipid particles (SNALP) and administered by intravenous injection. The SNALP formulation contained the lipids 3-N-[(ω-methoxypoly(ethylene glycol)₂₀₀₀)carbamoyl]-1,2-dimyristyloxy-propylamine (PEG-DMA), 1,2-dilinoleyloxy-N,N-dimethyl-3-qminopropanone (DLinDMA), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol.

8. The siRNA-LAT1 or siRNA-ASCT2 can be encapsulated in Injectin In Vivo SiRNa Delivery Reagent (BioCellChallenge SAS, Toulon, France) and administered by intravenous injection. The Injection formulation contained the following mixture: 10 μg of siRNA in 10 μL of glucose containing buffer, 40 μL with a sterile RNase-free water, 10 μL of Injectin reagent. The mixture should be mix by pipetting up and down and incubated 15 minutes at room temperature before injection.

Example 1

LAT1 and ASCT2 Immunoblotting in Human Cancer Cells

The presence of LAT1 protein and ASCT2 was studied by means of immunoblotting using an antibodies raised against LAT1 and ASCT2. As shown in FIG. 1, the antibody raised against LAT1 and ASCT2 recognized the presence of LAT1 and ASCT2 in all cancer cell lines.

Example 2

LAT1 and ASCT2 Gene Expression in Human Cancer Cells

The presence of LAT1 and ASCT2 mRNA was studied by means of Real-time PCR using primers against ASCT2. As shown in FIG. 2, LAT1 and ASCT2 gene expression relative to the house keeping gene GADPH was found in all cancer cell lines.

Example 3

[⁴C]-L-Leucine and [¹⁴C]-L-Alanine Uptake

Sodium-independent [¹⁴C]-L-leucine (0.25 μM) uptake at initial rate of uptake (1 min) in epithelial carcinoma cells was significantly (P<0.001) reduced by 3 mM unlabelled L-leucine as shown in FIGS. 3A-3D. Sodium-dependent [¹⁴C]-L-alanine (0.25 μM) uptake at initial rate of uptake (1 min) in epithelial carcinoma cells was significantly (P<0.01) reduced by 3 mM unlabelled L-alanine, as shown in FIGS. 3E-3H.

Example 4

LAT1 and ASCT2 Gene Expression in Human Cancer Cells

As shown in FIG. 4A, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 6, 22, 34, 58 and 61 (for example, an siRNA comprising or consisting of SEQ ID NO: 110, 126, 138, 162 and 165 respectively) decreased LAT1 mRNA relative abundance in liver carcinoma SK-HEP-1 cells at 24 h. The effects siRNA-LAT1 against nucleotide SEQ ID NO: 58 were significantly greater (p<0.05) than those with SEQ ID NO: 34. As shown in FIG. 4B, treatment for 6 h of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 225, 237, 267 and 278 (for example, an siRNA comprising or consisting of SEQ ID NO: 314, 326, 356 and 367 decreased ASCT2 mRNA relative abundance in liver carcinoma SK-HEP-1 cells at 24 h. The effects siRNA-ASCT2 against nucleotide SEQ ID NO: 278 were significantly greater (p<0.05) than those with SEQ ID NO: 267.

Example 5

[¹⁴C]-L-Leucine and [¹⁴C]-L-Alanine Uptake

As shown in FIGS. 5A and 5C, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 6, 22, 34, 58 and 61 (for example, an siRNA comprising or consisting of SEQ ID NO: 110, 126, 138, 162 and 165 respectively) decreased [¹⁴C]-L-leucine (0.25 μM) uptake at initial rate of uptake (1 min) in liver carcinoma SK-HEP-1 cells at 24 h and 48 h. The effects siRNA-LAT1 against nucleotide SEQ ID NO: 58 were significantly greater (p<0.05) than those with SEQ ID NO: 34. As shown in FIGS. 5B and 5D, treatment for 6 h of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 225, 237, 267 and 278 (for example, an siRNA comprising or consisting of SEQ ID NO: 314, 326, 356 and 367 for 24 h [¹⁴C]-L-leucine (0.25 μM) uptake at initial rate of uptake (1 min) in liver carcinoma SK-HEP-1 cells at 24 h and 48 h.

Example 6

Modifications of siRNA-LA T1 and siRNA-ASCT2

siRNA-LAT1 against nucleotide SEQ ID NOS 58 and 61 (for example, an siRNA comprising or consisting of SEQ ID NO: 162 and 165 respectively) are shown in FIG. 6. (5′ DNA sense, 5′ sense siRNA and 3′ antisense siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 58/387/388, 58/389/390, 58/389/412, 61/165/396, 61/391/392, 61/393/394 and 61/395/396). siRNA-ASCT2 against nucleotide SEQ ID NOS 267 and 278 (for example, an siRNA comprising or consisting of SEQ ID NO: 356 and 367 respectively) are shown in FIG. 7. 5′ DNA sense, 5′ sense siRNA and 3′ antisense siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 267/397/398, 267/399/400, 267/401/402, 278/367/408, 278/403/404, 278/405/406 and 278/407/408

Example 7

[¹⁴C]-L-Leucine and [¹⁴C]-L-Alanine Uptake

As shown in FIG. 8A, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 61/165/396, 58/387/388, 61/391/392 as described herein and the commercially available SI31011000 decreased [¹⁴C]-L-leucine (0.25 μM) uptake at initial rate of uptake (1 min) in fibrosarcoma HT-1080 cells at 48 h. As shown in FIG. 8B, treatment for 6 h of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 278/367/408, 267/397/398 and 278/403/404 (for example, an siRNA comprising or consisting of SEQ ID NO: 356, 367 or an siRNA comprising or consisting of SEQ ID NO: 399 as the sense strand and SEQ ID NO: 400 as the antisense strand or SEQ ID NO: 405 as the sense strand and SEQ ID NO: 406 as the antisense strand respectively) and the commercially available SI00097930 decreased [¹⁴C]-L-alanine (0.25 μM) uptake at initial rate of uptake (1 min) in fibrosarcoma HT-1080 cells at 48 h. The effects siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404 were significantly greater (p<0.05) than those with SEQ ID NO: 267/397/398.

Example 8

LAT1 and ASCT2 Gene Expression in Human Cancer Cells

As shown in FIGS. 9A and 9C, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 61/165/396, 58/387/388 and 61/391/392 (for example, an siRNA comprising or consisting of SEQ ID NO: 162, 165, or an siRNA comprising or consisting of SEQ ID NO: 387 as the sense strand and SEQ ID NO: 388 as the antisense strand or SEQ ID NO: 393 as the sense strand and SEQ ID NO: 394 as the antisense strand respectively) decreased LAT1 mRNA relative abundance in human colon cancer HTC-116 cells at 24 h or 48 h. As shown in FIGS. 9B and 9C, treatment for 6 h of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 278/367/408, 267/397/398 and 278/403/404 (for example, an siRNA comprising or consisting of SEQ ID NO: 356, 367, or an siRNA comprising or consisting of SEQ ID NO: 399 as the sense strand and SEQ ID NO: 400 as the antisense strand or SEQ ID NO: 405 as the sense strand and SEQ ID NO: 406 as the antisense strand respectively) decreased ASCT2 mRNA relative abundance in human colon cancer HTC-116 cells at 24 h or 48 h.

Example 9

LAT1 Gene Expression in Human Cancer Cells

As shown in FIGS. 10A and 10B, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 (for example, an siRNA comprising or consisting of SEQ ID NO: 387 as the sense strand and SEQ ID NO: 388 as the antisense strand) decreased LAT1 mRNA relative abundance in human colon cancer HTC-116 cells in a concentration dependent manner and when using 0.5% Lipofectamine 2000®, Lipofectamine RNAiMAX® or Injectin® as the transfecting agents at 72 h.

Example 10

Cell Proliferation of Human Colon Cancer HTC-116 Cells, Transfection Agents and Negative Controls

As shown in FIG. 11A, treatment for 6 h of human colon cancer HTC-116 cells with 0.5% Lipofectamine 2000® for 72 h did not affect cell proliferation. By contrast, treatment of human colon cancer HTC-116 cells with Injectin® did affect cell proliferation at 72 h in a statistically significant manner at 0.1%, 0.113 and 0.115%, as shown in FIG. 11B. Injectin is a lipid based siRNA transfection agent. Manufacture instructions recommend the use of 1 μg of siRNA per μL of Injectin® reagent (ratio 1:1) where the volume of Injectin reagent corresponds to 20% of the total complex mixture. For in vivo assays, siRNA:Injectin® complexes were prepared exactly as recommended by the producer. For in vitro assays, the siRNA concentration used was downscaled and therefore the maintenance of 20% of Injectin® in the total siRNA:Injectin® complex mixture was unviable. For such a reason, siRNA complexation efficacy and siRNA:Injectin® transfection efficiency were evaluated using different percentages of Injectin® in the complex mixture. Electrophoresis of siRNA:Injectin® complexes revealed that siRNA is fully complexed when the siRNA:Injectin® ratio is 1:1 and the percentage of Injectin® in the complex mixture is higher than 0.9% (FIG. 12A). However, siRNA complexation is not effective when the siRNA:Injectin® ratio 1:1 is maintained but the amount of Injectin® in the complex mixture is equal or lower than 0.2% (FIG. 12B). This data suggests that when the percentage of Injectin® in the complex is lower than 0.2% the recommended 1 μg of siRNA per μL of Injectin® ratio is no longer effective. Therefore, the amount of Injectin® per μg of siRNA needs to be increased in order to obtain a more efficient siRNA:Injectin® complex. Similarly, an increase in the amount of Injectin® in the complex mixture enhances the effect of siRNA sequences upon cell proliferation (FIG. 15), as evidence of the enhanced transfection efficiency of siRNA:Injectin® complexes with higher amounts of Injectin® in the siRNA transfection mixture. As shown in FIG. 13, negative control siRNA commercial (from QIAGEN) sequences NC-SI03650318 and NC-SI03650325 did not significantly affect the proliferation human colon cancer HTC-116 cells at 72 h exposure times using Injectin® (0.075 and 0.1%) or lipofectamine 2000 (0.25%) as the transfecting agent.

Example 11

Cell Proliferation of Human Colon Cancer HTC-116 Cells

As shown in FIG. 14A, treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 6, 22, 34, 58/162/411, 58/387/388, 58/389/390, 58/389/412, 61/165/396, 61/391/392, 61/393/394, 61/395/396 as described herein, and three commercially available siRNAs (SI31011000, HSS112005 and SASI_Hs01_00103513 respectively from QIAGEN, Thermofisher Scientific and Sigma-Aldrich) decreased cell proliferation at 72 h exposure times using 0.1% Injectin® as the transfecting agent. The effects siRNA-LAT1 against nucleotide SEQ ID NO: 58 were significantly greater (p<0.05) than those with SEQ ID NO: 34 and the effects of siRNA-LAT1 against nucleotide SEQ ID NOS 58/389/390 and 58/389/412 were significantly greater (p<0.05) than those with SEQ ID NO: 58. As shown in FIG. 14B, treatment for 6 h of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 267/397/398, 267/399/400, 267/401/402, 278/367/408, 278/403/404, 278/405/406, 278/407/408 as described herein, and one commercially available siRNA (SI00097930 from QIAGEN) decreased cell proliferation at 72 h exposure times using 0.1% Injectin® as the transfecting agent. The effects siRNA-ASCT2 against nucleotide SEQ ID NO: 267/397/398 and SEQ ID NO: 267/401/402 were significantly greater (p<0.05) than those with SEQ ID NO: 267/356/402 and the effects of siRNA-ASCT2 against nucleotide SEQ ID NO: 278/405/406 and SEQ ID NO: 278/407/408 were significantly greater (p<0.05) than those with SEQ ID NO: 278/367/408.

Treatment for 6 h of cells with the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 (for example, an siRNA comprising or consisting of SEQ ID NO: 387 as the sense strand and SEQ ID NO: 388 as the antisense strand), as shown in FIG. 15A, and siRNA-ASCT2 against nucleotide SEQ ID NOS 267/397/398 and 278/403/404 (for example, an siRNA comprising or consisting of SEQ ID NO: 399 as the sense strand and SEQ ID NO: 400 as the antisense strand or SEQ ID NO: 405 as the sense strand and SEQ ID NO: 406 as the antisense strand respectively), as shown in FIGS. 15B and 15C respectively, decreased cell proliferation at 72 h exposure times that was greater the higher the concentration Injectin® in the siRNA:Injectin® complexes. This was particularly evident with siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 and siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404.

Example 12

Cell Proliferation of Human Colon Cancer HTC-116 Cells in the Presence of Cytotoxic Antineoplastic Agents

As shown in FIG. 16, the effects of the cytotoxic antineoplastic agents 5-fluoruracil (5-FU; 3 and 10 μM), cisplatin (Cisp; 3 and 10 μM) and oxaliplatin (Oxa; 1 and 3 μM) alone upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times were all significantly enhanced in combination with the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388, as described herein, in a concentration dependent manner. As shown in FIG. 17A, the effects of the cytotoxic antineoplastic agents 5-fluoruracil (5-FU; 10 μM) alone upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times was enhanced by the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 as defined herein, but not by the siRNA-LAT1 against nucleotide SEQ ID NO: 61/391/392, as described herein. Similarly, as shown in FIG. 17B, the enhancement of effects by he cytotoxic antineoplastic agents 5-fluoruracil (5-FU; 10 μM) by the siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404, as described herein, was more marked than that by the siRNA-ASCT2 against nucleotide SEQ ID NO: 267/397/398, as described herein.

Example 13

Cell Proliferation of Human Colon Cancer HTC-116 Cells in the Presence Anti-LA T1 and Anti-ASCT2 siRNAs

As shown in FIG. 18A, the significant decrease upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times by the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388, as described herein, was enhanced by the siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404, as described herein, at non-efficacious conditions (0.037% Injectin®). Similarly, as shown in FIG. 18B, the significant effects upon proliferation of human colon cancer HTC-116 cells at 72 h exposure times by the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388, as described herein, was enhanced by the siRNA-ASCT2 against nucleotide SEQ ID NO: 267/397/398, as described herein, at non-efficacious conditions (0.037% Injectin®).

Example 14

LAT1 and ASCT2 Gene Expression and Cell Proliferation of Human Colon Cancer HTC-116 Cells in the Presence Anti-LAT1 and Anti-ASCT2 siRNAs

As shown in FIG. 19A, treatment of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 58/387/388, 58/389/390, 61/165/396, 61/391/392, 61/393/394 as described herein, and two commercially available siRNAs (SI31011000 and HSS112005, respectively from QIAGEN and Thermofisher Scientific) for 6 h significantly decreased LAT1 mRNA relative abundance in human colon cancer HTC-116 cells though evidently with siRNA-LAT1 against nucleotide SEQ ID NOS 58/387/388 and 58/389/390. As shown in FIG. 19B, treatment of cells with the siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 58/387/388, 58/389/390, 61/165/396, 61/391/392, 61/393/394, as described herein, and two commercially available siRNAs (SI31011000 and HSS112005, respectively from QIAGEN and Thermofisher Scientific) for 6 h significantly decreased proliferation of human colon cancer HTC-116 cells at 72 h, though evidently with siRNA-LAT1 against nucleotide SEQ ID NOS 58/162/411, 58/387/388 and 58/389/390.

As shown in FIG. 20A, treatment of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 267/397/398, 267/399/400, 278/367/408, 278/403/404, 278/405/406, as described herein, and one commercially available siRNAs (SI00097930 from QIAGEN) for 6 h significantly decreased ASCT2 mRNA relative abundance in human colon cancer HTC-116 cells though evidently with siRNA-LAT1 against nucleotide SEQ ID NOS 267/397/398 and 278/403/404. As shown in FIG. 20B, treatment of cells with the siRNA-ASCT2 against nucleotide SEQ ID NOS 267/356/402, 267/397/398, 267/399/400, 278/367/408, 278/403/404, 278/405/406, as described herein, and one commercially available siRNAs (SI00097930 from QIAGEN) for 6 h significantly decreased proliferation of human colon cancer HTC-116 cells at 72 h, though evidently with siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404.

Example 1

LAT1 and ASCT2 Immunoblotting in the Xenograft Tumour Model

The presence of LAT1 protein and ASCT2 was studied by means of immunoblotting using an antibodies raised against LAT1 and ASCT2. As shown in FIG. 21, the antibody raised against LAT1 and ASCT2 recognized the presence of LAT1 and ASCT2 in both tumours (T1 and T2) derived from human colon cancer HTC-116 cells.

Example 16

LAT1 and ASCT2 Gene Expression in Human Cancer Cells

The presence of LAT1 and ASCT2 mRNA was studied by means of Real-time PCR using primers against LAT1 and ASCT2. As shown in FIG. 22, LAT1 and ASCT2 gene expression relative to the house keeping gene GADPH was found in both tumours (T1 and T2) derived from human colon cancer HTC-116 cells.

Example 17

Tumour Growth

As shown in FIG. 23, the relative tumour volume in the xenograft tumour model developed in immune deficient mice injected subcutaneously with human colon cancer HTC-116 cells and treated every other day with intratumoral injections (50 μL) of vehicle (Injectin®) or the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 (10 μg) and the siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404 (10 μg), as described herein. The reduction in relative tumour volume by the siRNA-LAT1 against nucleotide SEQ ID NO: 58/387/388 (10 μg) and the siRNA-ASCT2 against nucleotide SEQ ID NO: 278/403/404 was statistically significant with p values of 0.0018 and 0.0051, respectively.

CONCLUSION

The treatment of cancer cells expressing LAT1 and/or ASCT2 transporter with siRNA-LAT1 and/or siRNA-ASCT2 leads to a decrease in LAT1 and/or ASCT2 protein and a decrease in [¹⁴C]-L-leucine uptake and [¹⁴C]-L-alanine uptake, which is accompanied by a decrease in cell proliferation. The decrease in cell viability and proliferation of cancer cells induced by the siRNA-LAT1 and/or the siRNA-ASCT2 is accompanied by apoptosis and a decrease in tumour growth and metastasis potential, as evidenced in nude mice subcutaneous tumours of human colon cancer HTC-116 cells.

Additional aspects of the invention will be apparent to those skilled in the art, or may be learned from the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

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The invention claimed is:
 1. An siNA (short interfering nucleic acid) molecule that can reduce expression of a LAT1 gene in a cell, wherein said molecule comprises a nucleic acid sequence selected from SEQ ID NO: 152, 153, 159, 162 and 184, or a nucleic acid sequence that differs from one of SEQ ID NO: 152, 153, 159, 162 and 184 by no more than one nucleotide, or said molecule comprises a nucleic acid sequence that is perfectly complementary to the full length of a sequence selected from SEQ ID NO: 152, 153, 159, 162 and 184, or is a variant thereof that differs from the perfectly complementary nucleic acid sequence by no more than 1 nucleotide.
 2. An siNA molecule of claim 1, wherein said molecule is between 19 and 25 base pairs in length.
 3. An siNA molecule of claim 1, wherein the siNA is selected from dsRNA, siRNA or shRNA.
 4. An siNA molecule of claim 3, wherein the siNA is siRNA.
 5. An siNA molecule of claim 1, wherein the siNA comprises 5′ and/or 3′ overhangs.
 6. An siNA of claim 1, wherein the siNA comprises at least one chemical modification.
 7. A pharmaceutical composition comprising at least one siNA of claim 1 and a pharmaceutically acceptable carrier.
 8. A nucleic acid construct or vector comprising a nucleic acid sequence encoding an siNA of claim
 1. 9. An siNA molecule, where said molecule comprises a sense sequence with a nucleic acid sequence selected from SEQ ID Nos 387 and 389 or a nucleic acid sequence that differs from one of SEQ ID Nos 387 and 389 by no more than one nucleotide, and an antisense sequence with a nucleic acid sequence selected from SEQ ID Nos 388, 390, and 412 or a nucleic acid sequence that differs from one of SEQ ID Nos 388, 390, and 412 by no more than one nucleotide. 